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Genetics are awesomeeee.
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Genetics are awesomeeee. Structure of DNA Each DNA molecule is made up of two very long polymers Double helix: is the shape Nucleotides: are the building blocks ... – PowerPoint PPT presentation
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Title: Genetics are awesomeeee.
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Genetics are awesomeeee.
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Structure of DNA
- Each DNA molecule is made up of two very long
polymers - Double helix is the shape
- Nucleotides are the building blocks
- deoxyribose ( a 5 carbon sugar)
- phosphate group
- nitrogenous base
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DNA double helix
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Nitrogenous bases
- There are four different nitrogenous bases
thymine (T), cytosine (C), - adenine (A), and guanine (G)
- These four bases are the foundation of the
genetic code. - These chemicals act as the cell's memory,
instructing it on how to synthesize enzymes and
other proteins. These four nucleotides encode
everything an organism needs to live and protects
this information with incredible accuracy.
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- In a human being
- DNA is broken down onto 46 separate chromosomes
- Each chromosome has about 160 million nucleotide
pairs - This massive amount of information is stored and
replicated almost flawlessly!
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DNA Replication
- INTERPHASE Before a cell divides, its DNA is
replicated - Semi Conservative replication Two strands of a
DNA molecule are separated, each ONE can be used
as a template to produce a complementary strand.
- Each template and its new complement together
then form a new DNA double helix, identical to
the original.
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- Before replication can occur, the length of the
DNA double helix about to be copied must be
unwound. INTERPHASE - The two strands must be separated, much like the
two sides of a zippper helicase - The enzyme DNA polymerase then moves along the
exposed DNA strand, joining newly arrived
nucleotides into a new DNA strand that is
complementary to the template.
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Meiosis I
- STEP ONE MEIOSIS I This is basically like the
PMATI of a regular mitosis. - Pairs of chromosomes are lined up at the center
of the cell and then (separated) and pulled to
each side. - Meiosis is a bit different because there is
something called crossing-over. This crossing
over is an exchange of genes from 1 homologous
chromosome to the other (genes from the
chromosome you got from mom go onto the
chromosome you got from dad. The genes are mixed
up, not resulting in a perfect duplicate like
mitosis. - This is why your children will not look exactly
like their Nana or Grandpa. They will look like
a combo.
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- The cell divides, leaving two new cells with a
pair of chromosomes each. Normally the cell would
begin to go about its business of living and
slowly duplicate the chromosomes for another
mitotic division. Since this is meiosis, there is
a very short interphase and division begins
again. The DNA is not doubled
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Meiosis II
- STEP TWO MEIOSIS II
- In Metaphase II all of the chromosomes line up
along the center of the cell - Anaphase II shows the chromosomes split and move
to opposite sides of the cell. - They don't divide up the DNA between the new
cells - Each daughter cell will get one-half of the DNA
- The cell membrane begins to pinch. When it's all
over, you are left with four haploid cells that
are called gametes. The eventual purpose of the
gametes will be to find other gametes with which
they can combine. When they do, they will form a
new organism.
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Mendels First Law
- Mendel's First Law is the law of "Segregation of
Characteristics. - Humans are Diploid. This means you get two
alleles for each trait. You get one allele from
mom and one allele from dad. - This law basically says that you can only get ONE
allele from mom. Only ONE from dad. - In eye color B Brown is dominant. Blue (b) is
recessive. - If mom has Brown eyes she could be BB or Bb. She
can only pass ONE allele on in her egg.
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Independent assortment
- Mendel's Second Law is the law of "Independent
Assortment". This says that for two
characteristics the genes are inherited
independently. - Example Your shoe size and hair color are not
inherited together. Meaning people with black
hair do NOT necessarily have Big Feet.
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- - If mom had the genotype AaBb she would make
four kinds of gametes(eggs) they would contain
the combinations of either AB, Ab, aB or ab. - A is dominant (big feet) a is recessive (little
ft) - B is dominant (black hair)b is recessive(blond)
- So, mom would pass on either
- Big feet black hair (AB),
- big feet and blonde hair (Ab)
- Little feet and black hair (aB)
- Little feet and blonde hair (ab)
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Punnett Square
- A punnett square is used to predict an expected
outcome of - a particular cross or
- breeding experiment.
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Non Mendelian Genetics
- Some traits are not passed on the way the traits
Mendel studied were. - Incomplete dominance
- Co dominance
- Multiple alleles
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Incomplete Dominance
- Incomplete dominance is a form of intermediate
inheritance in which one allele for a specific
trait is not completely dominant over the other
allele. This results in a combined phenotype.
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Codominance
- A condition in which both alleles of a gene pair
in a heterozygote are fully expressed, with
neither one being dominant or recessive to the
other.
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Multiple Alleles
- Any set of three or more alleles or alternative
states of a gene. - Only two of which can be present in an organism
at a time. - Responsible for differences in expressions of a
given trait. Example brown eyes v. green eyes.
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