The Living Environment

1
The Living Environment

• The study of organisms and their interactions
  with the environment.

2
Topics

• Unit 1 Ecology
• Unit 2 The Cell
• Unit 3 Genetics
• Unit 4 History of Biological Diversity
• Unit 5 The Human Body

3
GENETICS

• The science of heredity and the study of how
  traits are passed on from generation to
  generation.

4
Mendelian Genetics How Genetics
Began

• Commonly referred to as the father of modern
  genetics Gregor Mendel, born in 1822 in what is
  now the Czech Republic, published the first known
  findings of heredity in 1866.
• His primary findings were based on the study of
  pea plants during his 14 year tenure as an
  Austrian monk in charge of the monastery garden.

5
Mendelian Genetics

• While tending his plants, Mendel was intrigued by
  the pea plants because he noticed that some were
  tall while others were short some had white
  flowers and some had purple flowers some had
  green peas and others had yellow peas.
• Mendel was determined to try to figure out what
  determined these different traits as well as
  others and began experimenting.

6
Plant Sexual Reproduction

• Pollen, produced by the anther, is transferred to
  the stigma, travels down the style into the
  ovary, and fertilizes the ovule producing a seed.
• Self-pollination occurs when pollen is
  transferred to the stigma of the same plant.
• Cross-pollination occurs when pollen is
  transferred to the stigma of another plant.

7
Mendelian Genetics

• Mendel began cross pollinating plants with
  similar traits and plants with varying traits and
  recording the outcomes of these crosses in a
  journal.
• From these various crosses performed over many
  years, Mendel concluded that traits are passed on
  from one generation to the next and wrote three
  laws regarding his findings.

8
Mendelian Genetics

• The Law of Dominance states that certain traits
  exhibit dominance over others which are said to
  be recessive.
• In other words, if two different alleles of the
  same trait are combined to form offspring, all of
  the offspring will exhibit the dominant allele.
• The only way for the offspring to express the
  recessive allele would be for both inherited
  alleles to be the recessive form of the trait.

9
Mendelian Genetics

• The Law of Segregation, later proven by the
  discovery of the process of meiosis, states that
  each gamete, produced by each parent, receives
  only one allele of each trait thus the alleles
  of each trait are segregated amongst the gametes.
• In other words, each sperm and egg produced only
  carries one allele for each trait resulting in
  offspring who receive one allele of each trait
  from each parent.

10
Review of Meiosis

• Recall that meiosis results in four daughter
  cells each containing half the number of
  chromosomes as the original cell and half the
  alleles of each gene.
• These daughter cells are also genetically
  different from the parent cell and from each
  other due to cross-over that occurs during
  prophase of meiosis I.

11
Mendelian Genetics

• The Law of Independent Assortment states that
  traits are inherited independently of each other.
• For example, with Mendels pea plants, the trait
  for plant height is inherited separately from the
  trait for pea color or flower color.
• This law does not apply to all traits in all
  organisms as some traits are genetically linked
  and are inherited together.

12
Probability and Punnett Squares

• A genotype is a pair of letters representing a
  particular genetic makeup, or type of genes.
  These letters are chosen based on the dominant
  allele.
• A phenotype is the physical characteristic
  exhibited by the organism as a result of its
  genotype.
• An organisms phenotype is dependant on its
  genotype.

13
Probability and Punnett Squares

• A homozygous pair of alleles is represented by
  any two of the same letters, either both capital
  or both lowercase. This is known as a purebred
  trait, where both alleles are identical.
• It is possible for a homozygous trait to be
  dominant or recessive.
• A heterozygous pair of alleles is represented by
  two different letters, one capital and one
  lowercase. This is known as a hybrid trait and
  will always exhibit the dominant phenotype.

14
Probability and Punnett Squares

• In the early 1900s Dr. Reginald Punnett
  developed the Punnett Square to predict the
  possible offspring of a cross between two known
  genotypes.
• Mendels journals show that even he was able to
  produce the ratios of offspring that we can now
  easily calculate using Punnett Squares.

15
Probability and Punnett Squares

• A monohybrid cross is a cross involving hybrids
  of a single trait.
• A monohybrid cross of the F1 generation will
  always result in 75 of the offspring exhibiting
  the dominant trait.
• A monohybrid cross results in a genotypic ratio
  of 121 and a phenotypic ratio of 31.

16
Probability and Punnett Squares

• A dihybrid cross is a cross involving hybrids of
  two different traits at the same time using a
  single Punnett Square.
• A dihybrid cross results in a genotype and
  phenotypic ratio of 9331.
• Dihybrid crosses can be used to prove Mendels
  Law of Independent Assortment.

17
Incomplete Dominance

• Cases in which one allele is not completely
  dominant over another are called incomplete
  dominance.
• These traits are sometimes referred to as
  blending traits.
• Examples include pink carnations and palomino
  horses.

18
Examples of Incomplete Dominance


19
Codominance

• Codominance occurs when both alleles (from each
  parent) contribute to the phenotype of the
  offspring because neither is dominant.
• Codominance results in a heterozygous (hybrid)
  organism such as a roan cow which has both red
  and white hairs.

20
Polygenic Traits

• Traits controlled by two or more genes are called
  polygenic traits.
• Polygenic traits often result in a wide range of
  phenotypes such as the range of eye colors or the
  range of skin tones in humans.

21
The Discovery of DNA

• Although Mendels journals were discovered around
  the turn of the 20th century, scientists lacked
  the technology to perform genetic research in any
  greater detail than Mendel himself until about
  1940.
• In 1944, Oswald Avery and his team determined
  that genes were composed of biochemical molecules
  called DeoxyriboNucleicAcid (DNA).

22
DNA as a Double Helix

• In 1951, Linus Pauling and Robert Corey
  determined that proteins like those found in the
  DNA molecule were a helical type of structure.
• In 1952, Rosalind Franklin using a technique
  called X-Ray diffraction took a picture of the
  DNA molecule.
• In 1953, James Watson and Francis Crick developed
  the double-helix model of the structure of DNA.

23
DNA The Double-Helix

• DNA, sometimes referred to as a twisted ladder or
  spiral staircase, is a very long chain molecule,
  consisting of sub-units called nucleotides.
• Each nucleotide is made up of three basic
  structures
• A sugar called deoxyribose
• A phosphate group
• A nitrogenous base

24
DNA Structure

• The backbone of the DNA structure, or side rails,
  are formed by the sugar-phosphate groups of each
  nucleotide.
• Connecting the two rails of the DNA structure are
  four types of nitrogenous bases
• Thymine (T)
• Adenine (A)
• Cytosine (C)
• Guanine (G)

25
DNA Structure

• The side rails of the twisted ladder are attached
  by the pairing of the nitrogenous bases extending
  from each side of the DNA molecule, creating the
  rungs of the ladder.
• Adenine always pairs with Thymine, while Guanine
  always pairs with Cytosine, thus creating the
  base pairs
• A T
• G C

26
DNA Structure
27
Chromosome Structure

• Chromosomes consist of
  tightly packed coils of
  
  DNA called chromatin.
• Chromatin consists of a
  
  DNA molecule tightly
  wound around
  proteins
  called histones.
• DNA consists of
  
  nucleotides which code
  for
  individual genes.
• Chromosome Chromatin DNA
  Gene Largest
  Smallest
• Chromosome Chromatin DNA
  Nucleotide

28
DNA Replication

• During DNA replication, the DNA molecule
  separates into two strands, then produces two new
  complimentary strands following the rules of base
  pairing.
• Each strand of the double-helix serves as a
  template for the new strand.

29
DNA Replication

• DNA replication is carried out by a series of
  enzymes.
• These enzymes unzip the DNA
  molecule by breaking the bonds of
  the base pairs, then synthesize a
  complimentary strand of DNA for
  each of the original strands.

30
DNA Replication
31
The Structure of RNA

• RNA, like DNA, consists of a long chain of
  nucleotides, each made up of a sugar, phosphate
  group, and a nitrogenous base.
• RNA differs from DNA in three main ways
• The sugar is ribose.
• RNA is single stranded.
• RNA contains Uracil (U) in place of Thymine.

32
Function of RNA in Cells

• The primary function of RNA in cells is protein
  synthesis.
• The assembly of amino acids into proteins is
  controlled by RNA.
• The three main types of RNA are
• mRNA (messenger)
• rRNA (ribosomal)
• tRNA (transfer)

33
Protein Synthesis

• RNA is produced within a cell from a strand of
  DNA through a process called transcription.
• mRNA is transcribed in the nucleus, enters the
  cytoplasm, and attaches to a ribosome.
• Next, translation of the mRNA strand occurs with
  assistance from tRNA within the ribosome,
  synthesizing proteins from amino acids.

34
Protein Synthesis

• Proteins are made by joining amino acids into
  long chains called polypeptides.
• Each polypeptide consists of a combination of any
  or all of the 20 different amino acids.
• The properties of these proteins are determined
  by the order in which the amino acids are joined
  to form the polypeptides.

35
The Genetic Code

• The language of mRNA instructions is called the
  genetic code.
• This code is written in a language that has only
  four letters, AUCG.
• The code is read three letters at a time so that
  each word of the coded message is three bases
  long.
• Each three letter word is known as a codon.

36
The Genetic Code

• A codon consists of three consecutive nucleotides
  that specify a single amino acid that is to be
  added to the polypeptide.
• There are 64 possible three-base codons.
• Some amino acids can be specified by more than
  one codon.

37
(No Transcript)
38
Amino Acids
39
The Roles of RNA and DNA

• DNA acts as the master plan and is stored
  safely within the nucleus of the cells of an
  organism.
• DNA controls every action of a cell and
  essentially every characteristic of an organism
  by producing blueprints in the form of RNA
  which will translate into proteins that control
  cellular functions and characteristics.

40
Genetic Mutations

• Mutations are changes in the DNA sequence that
  affect genetic information.
• Gene mutations result from changes in a single
  gene.
• Chromosomal mutations involve changes in whole
  chromosomes.
• Mutations can be beneficial to an organism,
  deleterious to an organism, or have no effect at
  all.

41
Gene Mutations

• Mutations that affect one nucleotide are called
  point mutations.
• Some point mutations substitute one nucleotide
  for another, resulting in a change in the
  translated amino acid in a protein.

42
Gene Mutations

• If a nucleotide is inserted or deleted, a
  frameshift mutation can occur.
• Frameshift mutations typically result in big
  changes in the translated amino acids of the
  protein, often altering the protein so it is
  unable to perform its normal functions.

43
Chromosomal Mutations

• Chromosomal mutations involve changes in the
  number or structure of chromosomes.
• These mutations can result in the deletion of
  genes from chromosomes, the inversion of genetic
  code, translocation, and duplication of genes on
  chromosomes.

44
Human Traits

• A pedigree is a diagram used to show how a
  particular genetic trait is passed down from
  generation to generation a genetic family tree.
• Squares represent males and circles represent
  females. A horizontal line connecting a square
  and circle illustrates a parental generation.
  Siblings are always drawn with the oldest to the
  left, youngest to the right.

45
Pedigrees

• Pedigrees can illustrate carriers of a genetic
  trait, as well as those exhibiting the effects of
  the trait.
• Fully shaded squares/circles represent
  individuals who exhibit the trait. (Homozygous
  dom./rec.)
• Half shaded squares/circles represent individuals
  who carry the trait but who do not exhibit the
  effects of the trait. (Heterozygous)

46
Pedigree of the Royal Family
47
Human Heredity

• A karyotype is a micrograph of the pairs of
  homologous chromosomes, taken during mitosis.
• Human cells each contain 22 pairs of autosomes
  and one pair of sex chromosomes equaling a total
  of 23 pairs (or 46) total chromosomes.
• Females have identical sex chromosomes (XX) while
  males have two different sex chromosomes (XY).

48
Autosomal Recessive Disorders
49
Autosomal Dominant Disorders
50
Sex-linked Genes

• Many genes are found on the X and Y chromosomes
  and are therefore referred to as sex-linked
  genes.
• More than 100 sex-linked disorders have been
  mapped on the X chromosome.
• Sex-linked disorders include
• Colorblindness
• Hemophilia
• Duchenne Muscular
  Dystrophy

51
Colorblind Test
52
Sex-linked Disorders
53
Chromosomal Disorders

• A typical chromosomal disorder results from an
  error during meiosis called non-disjunction when
  chromosomes do not separate evenly resulting in
  trisomy, or three copies of a particular
  chromosome instead of the usual two copies.
• Non-disjunction
  typically leaves
  
  some gametes
  
  containing only one
  
  copy of a
  
  chromosome,
  
  known as
  monosomy.

54
Chromosomal Disorders

• Alterations of chromosome number are serious,
  often fatal disorders.
• Down Syndrome, or trisomy 21, occurs due to
  non-disjunction resulting in offspring with 47
  chromosomes an extra chromosome 21.

55
Chromosomal Disorders

• Non-disjunction in sex chromosomes can lead to
  disorders such as Turners Syndrome (X) and
  Kleinfelters Syndrome (XXY).
• Individuals with either of these disorders are
  sterile and therefore cannot reproduce and pass
  on their genetic disorder.

56
Extra Genetic Material Disorders
57
Chromosomal Disorders

• Cri-du-chat is a genetic deletion disorder
  whereby a part of the 5 chromosome was deleted
  during DNA replication.
• Typical effects of this disorder include mental
  retardation, pinched facial characteristics, and
  a cat-like cry.

58
Genetic Deletion Disorders
59
Multifactorial Chromosome Abnormalities
60
DNA Analysis

• Gel electrophoresis is a technique used to
  separate DNA fragments.
• Separating DNA fragments is useful in mapping a
  DNA fingerprint in order to solve criminal
  investigations and to perform genomic evaluations.

61
Gel Electrophoresis

• DNA is extracted from a cell(s), then cut into
  segments using a restriction enzyme.
• The DNA segments are then separated using gel
  electrophoresis.
• The segments are injected into wells at one end
  of an agarose gel.
• Once electricity is applied across the gel, the
  segments of DNA will spread across the gel.

62
Gel Electrophoresis
63
Gel Electrophoresis

• These segments can be viewed under UV light.
• A special camera is then used to photograph the
  gel for comparison purposes or for use in court.

64
DNA Fingerprinting

• Short segments will travel further down the gel
  while long segments will stay closer to the
  wells.
• DNA fingerprinting can be used to identify a
  suspect in a criminal investigation or determine
  the father of a child.

65
Human Genome Project

• The Human Genome Project began
  in 1990, headed up in the US by
  James
  Watson, and was completed
  in June 2000, after a
  collaborative
  effort by geneticists around the
  globe.
• The goal was to determine the sequence of base
  pairs for the entire human genome and map all
  30,000 genes in a human DNA strand.

66
Key Findings of the Project

• 1. There are approx. 30,000 genes in human
  beings, the same range as in mice and twice that
  of roundworms. Understanding how these genes
  express themselves will provide clues to how
  diseases are caused.
• 2. All human races are 99.99  alike, so racial
  differences are genetically insignificant. This
  could mean we all descended from the original
  mother who was from Africa.
• 3. Most genetic mutation occur in the male of the
  species. So men are agents of change. They are
  also more likely to be responsible for genetic
  disorders.
• 4. Genomics has led to advances in genetic
  archaeology and has improved our understanding of
  how we evolved as humans and diverged from apes
  25 million years ago. It also tells how our body
  works, including the mystery behind how the sense
  of taste works.

67
Genetic Engineering

• Genetic engineering is the purposeful altering or
  selection of certain traits in an organism.
• Selective breeding is an indirect method of
  genetic engineering.
• Selective breeding is the purposeful mating of
  organisms with particular traits in order to
  produce offspring that exhibit the desired
  trait(s).

68
Genetic Engineering

• Hybridization is a method of selective breeding
  whereby two parents, each exhibiting different
  desired traits are crossed to produce a more
  desirable product.
• Inbreeding is the continued breeding of
  individuals with the desired characteristics,
  typically between members of the same family or
  same group of offspring.

69
Genetic Engineering Manipulating DNA

• DNA can be cut and pasted to form a new strand
  of DNA called recombinant DNA.
• Enzymes are used to cut and paste the strands of
  DNA.
• PCR is a technique used to build recombinant DNA.
• The recombinant DNA can then be inserted into an
  organism, thus altering their genetic code.

70
Genetic Engineering Cell Transformation

• During transformation, a cell takes in DNA from
  outside the cell.
• This external piece of DNA becomes part of the
  cells DNA.
• Plasmids are small, circular DNA molecules
  commonly found in bacteria.
• Once reinserted into bacterial cells, those cells
  can be used to transform other cells.

71
Genetic Engineering Cell Transformation

• Bacteria cells containing the recombinant DNA
  plasmid can be used to alter the DNA in plant or
  animal cells in order to alter that organisms
  genetic code.
• This procedure might be performed to genetically
  engineer a plant to have better resistance to
  insects or a cow to produce more milk.

72
Genetic Engineering Cell Transformation
73
Genetic Engineering Transgenic Organisms

• Transgenic organisms are genetically engineered
  organisms, created by inserting a gene(s) from
  one organism into another.
• Genetically modified organisms are created to
  study various traits in different organisms as
  well as to produce more useful organisms such as
  livestock that produce more growth hormone.

74
Genetic Cloning

• Genetic cloning involves the artificial
  reproduction of an organism that will be
  genetically identical to its parent organism.
• The first organism reported as being successfully
  cloned was a sheep named Dolly, reportedly
  cloned in Scotland in 1996.

75
Genetic Cloning

• Dolly was cloned by inserting the DNA from a
  somatic cell of one sheep into the egg cell,
  whose nucleus had been removed, of another sheep
  then electrically stimulating the egg and
  implanting the embryo into the uterus of the
  surrogate mother.

76
Genetic Cloning

• It has long been theorized that extinct organisms
  might be resurrected if we could collect the
  organisms DNA from fossilized remains.
• The recently discovered baby mammoth will soon
  undergo a cloning-like process in an attempt to
  resurrect this long extinct creature.
• However, an ethical question must first be
  answeredshould it be done if we can manage to do
  it?
• Mammoth Resurrection