Genetics

1
Genetics
2
DNA MOLECULE The Code of LIFE

• What is DNA?
• DNA DeoxyriboseNucleic Acid
• Molecule that makes up genes
• Determines traits in all living things

3
What does DNA look like?

• Twisted ladder
• Spiral stair case
• http//learn.genetics.utah.edu/content/begin/tour/
  index.html

4
6 Features of DNA

• 1. two main sides (ladder uprights)
• 2. sides are two alternating chemicals
• A sugar
• An acid
• 3. parts connect the uprights (ladder rungs)
• 4. Nitrogen bases form the rungs
• 5. 4 different nitrogen bases
• Adenine (A) -- Thymine (T)
• Guanine (G) -- Cytosine (C)
• 6. Pairing
• A can only pair with T
• C can only pair with G
• These fit together like a puzzle

5
Where is DNA found in the cell?

• Found in the nucleus
• It makes up chromosomes

6
What is a GENE?

• Short piece of a chromosome that determines
  traits
• Gene has a specific number of DNA base pairs on a
  chromosome
• http//learn.genetics.utah.edu/content/begin/dna/t
  our_gene.html
• http//www.fofweb.com/Science/default.asp?ItemIDW
  E40

7
chromosome Number

• Human sperm or egg cell has 23 chromosomes
  (Meiosis)- not paired
• Body cells have 46 chromosomes (23 pairs)
  (MITOSIS)
• Different organism have different number of
  chromosomes
• Carrot plant 18 chromosomes 9 pairs
• Corn plant 20 chromosomes 10 pairs
• Rabbit 44 chromosomes 22 pairs

8
What is an Amniocentesis?

• A needle is inserted into a pregnant womans
  abdomen
• Remove a liquid called amniotic fluid
• Fetal cells are in the liquid
• Happens at 14-16 weeks
• Analyze fetal cells
• Match up chromosome pairs to make a karyotype
• http//www.youtube.com/watch?vfvqJ4lX5I8o

9
Karyotype - A set of photographs of chromosomes
grouped in order of pairs
10
Karyotype
11
Sex- a genetic trait

• Sex chromosomes chromosomes that determine the
  sex of a organism (male or female)
• XX female
• XY male
• Females can only give an X (only an X in ovary)
• Males can give an X or Y in sperm
• Males determine the sex of the offspring
• ONLY MALES HAVE Y CHROMOSOME
• Autosomes all other chromosomes EXCEPT sex
  chromosomes (DONT DETERMINE THE SEX)
• http//learn.genetics.utah.edu/content/begin/tour/
  index.html

12
Chances of having a boy or girl

• Mother
• X X
  
• X
• Y
• Father sex

13
Genetic Vocabulary http//learn.genetics.utah.edu
/content/begin/tour/index.html

• Genetics
• The study of how traits are passed through
  reproduction/fertilization from parent to
  offspring
• Trait
• A feature or quality that an animal, plant, or
  other organism has or shows
• Gene
• Small section of a chromosome that determines a
  specific trait
• Examples
• Eye color, height, freckles,
• Allele
• Different form of a gene can be dominant or
  recessive
• Every gene contains 2 alleles

14

• Dominant Allele
• Allele that allows a trait to be expressed while
  keeping other alleles from showing
• Recessive Allele
• Allele that gets overpowered by or masked by a
  dominant allele for the same trait
• Present but not expressed
• Each organism receives ONE allele for each trait
  from each parent
• ½ of the alleles come from the egg (mom)
• ½ of the alleles come from the sperm (dad)

15

• Homozygous Pure both alleles are the SAME
• Homozygous Dominant
• Both alleles are dominant and are written with
  capital letter
• Ex. TT Tall BB Brown eyes
• Homozygous Recessive
• Both alleles are recessive and are written with
  lower case letters
• Ex. tt short bb blue eyes
• Heterozygous
• Different two alleles for the same trait are
  different
• One recessive and one dominant
• The dominant trait gets expressed
• Ex. Tt Tall Bb brown eyes

16

• Genotype
• The combination of alleles or genes
• Represented with letters
• Ex. TT Tt tt
• Phenotype
• Physical appearance or expression of alleles or
  genotypes
• Ex. Tall Tall Short

17
Punnett Square

• Prediction of what genes can combine when egg and
  sperm join (FERTILIZATION)
• Review
• F dominant gene FF pure dominant
• f recessive gene Ff heterozygous
• ff
  pure recessive

18
5 steps to Punnett Squares

• 1. Draw your punnett square
• 2. Decide which genes will be moms sex cells
  and which will be dads.
• Ex. Mom and Dad are heterozygous for
  Free-earlobes
• Ff x Ff Mom
• F f
  
  
• F
  
• Dad
• f

19
5 steps to Punnett Squares

• 3. Copy the letter that appear at the top of the
  square into the boxes below each letter
• Mom
• F f
  
• F
  
• Dad
• f
• 4. Copy the letters that appear at the side of
  the square into the boxes next to each letter
• Mom
• F f
  
• F
  
• Dad
• f

20
5 steps to Punnett Squares

• 5. Calculate the ratio of genotype of the
  offspring
• of pure dominant of heterozygous of pure
  recessive
• FF Ff ff
  (genotypic ratio)
• 1 2 1

21
Example

• What would the offspring look like if the mother
  was purely dominant for brown eyes and the father
  is heterozygous ? B brown dominant over b
  blue
• Moms genes ________ Dads genes ________
• Ratio of offspring

22
Incomplete Dominance

• Occurs when NEITHER gene is totally dominant to
  the other gene
• Results in a NEW trait, which is a BLEND of the
  dominant and recessive traits
• http//learn.genetics.utah.edu/content/begin/tour/
  index.html

23
Incomplete DominanceExamples

• Snap dragon color is incompletely dominant. Red
  flowers are dominant to white flowers. Pink
  flowers are the result of incomplete dominance
• What will the offspring be of a cross between
  homozygous red snapdragon and a homozygous white
  snapdragon?
• What will the results be of a cross between 2
  pink snapdragons?

24
Example of Incomplete Dominance

• Blood cell shape
• Normal shape Round (R)
• Recessive shape Sickle (R)
• Person with all round cells RR
• Person with all sickle cells RR
• Person with both types RR
• If a person has RR they have Sickle Cell
  Anemia
• Genetic disorder that causes serious health
  problems
• Blood cells cant transport oxygen well
• Blood cells cant move well through the body

25
Example of Incomplete Dominance

• If mom and dad are both heterozygous for blood
  cell shape, what are the chances they will
  produce a child with sickle cell anemia?

26
Blood Type in Humans

• Humans have 4 different blood types
• A,B,AB,O
• 3 genes control blood typing A,B,O
• Both A and B are DOMINANT to O (Recessive)
• A and B are not dominant to one another they are
  incompletely dominant (blend to for AB blood
  type)
• Most common blood type O
• Rarest blood type AB-
• Universal Donor Type O
• Universal acceptor Type AB
• Rh factor 85 ()/ 15 (-)

27
Blood Type Example

• If mom is homozygous recessive for O type blood
  and dad is type AB. What are the possible
  genotypes and phenotypes for their offspring?
•  

28
Genetic Disorders

• What causes a genetic disorder?
• Being born with a more or less chromosomes
• Having 47 chromosomes instead of 46
• Sex-linked- genes carried on the sex chromosome
• How can you be born with the wrong chromosome
  number?
• Chromosomes dont separate correctly when the sex
  cells are being made
• Chromosomes STICK together instead of separate
• Normal Sex Cell Formation

46
23
23
46
46
23
23
29

• Abnormal Sex Cell Formation
• If the chromosome pair that sticks together are
  the sex chromosomes the following will happen

45
23
46
22
47
24
23
XXY
Male
XX
Y
XX
Y
Y
Dies
X
XXY
XY
Male
XY
X
X
Female
30
Genetic Diseases

• Down Syndrome
• Born with an extra chromosome (chromosome 21)
• Slow learner
• Heart problems
• Hemophilia
• Recessive gene on the X chromosome (like
  colorblindness)
• Blood can not clot (missing Factor VIII)

31
Genetic Diseases

• Dyslexia
• Controlled by a gene on an autosome (non sex
  chromosome)
• Reverse letter b d, p q
• Reverse numbers 13 31
• Klinefelters Syndrome-
• XXY individual
• Male with abnormal proportions (large breasts,
  small testicles)

32
Color blindness- sex linked trait

• Red and Green colors look like shades of gray
• Trait is carried on the X chromosome
• Females (XX) have 2 genes to code for
  colorblindness
• Males (XY) have only 1 gene to code for
  colorblindness
• Dominant trait XC can separate red and
  green
• Recessive trait Xc can NOT separate red
  and green
• http//www.geocities.com/Heartland/8833/coloreye.h
  tml
• Males are more likely to be colorblind!

33
Color blindness- sex linked trait
34
Color blindness- sex linked traitExample

• If mom is a carrier for colorblindness and dad is
  unaffected.What are the chances of having a
  colorblind child?