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Flashcard Warm-up
Genotype vs.
Phenotype
Genotype is the genetic makeup (AA, Aa, or aa)
Phenotype is the physical trait, a result of the genotype
AlleleFor any trait, such as
hair color, there are different forms of the protein that create the different hair
colors. Each different form is called an allele. We use
capital letters to represent dominant
alleles and lower case letters to represent the
recessive alleles.
Unit 10- GeneticsWhere did my traits come from??
Inheritance of chromosomes
Egg + sperm zygote
egg
sperm
zygote
fertilizationmitosis &development
meiosis
Traits: physical or physiological characteristics; like eye color, or blood type◦Phenotype:
individual’s observable trait; brown hair
Genes: Portion of DNA that make proteins that control our traits and are found on chromosomes. ◦Chromosomes exist in
pairs, one from sperm one from egg.
Alleles: different versions of genes; blue eye gene, brown eye gene; we use letters to represent alleles◦Alleles are inherited
separately from each parent.
How does this work?
eye color(brown?)
hair colo
r
hair colo
r
eye color
(blue?)
Paired chromosomes have same kind of genes◦ but may be different alleles
Genes affect what you look like
X BB
bb
Bb
Bb
Bb
Bb
Where did the blue eyes go??
Genes affect what you look like…
X Bb
bb
Bb
Bb
bb
bb
Why did the blue eyes stay??
What is a genotype and how do we write it?Genotype: the genetic makeup
◦ (the alleles you received from mom and dad)
Examples of genotypes:Homozygous: Identical copies;
AA – homozygous dominant aa - homozygous recessive
◦Dominant genes mask or hide recessiveHeterozygous: one dominant and one
recessive; Aa2 people can have the same
appearance but have different genetics: BB vs Bb
Mendelian Genetics:
Gregor Mendel : Father of Genetics◦Studied pea plants--- 1866◦Why pea plants?
Mendel’s PrinciplesThree Principles: 1. Principle of Dominance: dominant alleles
can mask/ hide recessive alleles◦ Homozygous dominant: AA; Dominant trait is
expressed◦ Heterozygous: Aa; dominant masks/hides recessive
and is expressed◦ Homozygous recessive: aa; recessive trait is
expressed2. Principle of Segregation: to separate, each
parent can only pass on one allele per trait3. Principle of Independent Assortment: genes
on separate chromosomes are passed on independently from one another.
Principle of Segragation
Principle of Independent Assortment
Punnett squaresBb x Bb
male / sperm
fem
ale
/ e
gg
s
X
BB
Bb bb
BbB
b
B b
Flashcard Warm-upMendel’s Principles of
Inheritance:
Use your notes from yesterday to write down and briefly EXPLAIN the three principles
Punnett Squares
Monohybrid cross: a Punnett square involving only one trait; 4 boxes
Dihybrid cross: a punnett square involving two traits; 16 boxes
Flashcard Warm-Up Trait:
◦Free earlobes- dominant = F◦Attached earlobes- recessive = f
1. A woman has free earlobes, what are two possible genotypes she might have?
2. The genotype for a man is Ff, what is his phenotype?
3. What is a gene?
Flashcard Warm-up
CodominantIf two alleles are
codominant, they are equally strong. Both alleles would
be seen in the phenotype. An
example is crossing a black chicken with a white chicken and the offspring having
both black and white feathers.
Incompletely
DominantNeither allele is
dominant, so when both alleles are present they
mix or blend. These alleles are written with ONE letter that has a
prime ‘
Non Mendelian Genetics: Codominance:
Both alleles are equally dominant and will be expressed
Phenotype: 3 possibilities
Genotype: 2 Capital letters; BB, WW, or BW
Red hair is dominantRR
Roan is a mixture of red and white hair-RW
White hair is dominantWW
Codominant Example:Cross a black cow with a white
cow. Both hair colors are dominant.
Incomplete DominancePhenotype: neither allele is
completely dominant to mask the other
Genotype: heterozygous RR’ results in a blended phenotype , capital letters for both traits and use a prime ‘ symbol for one
RR RR’ R’R’
Incomplete Dominance ExampleCross a white flowered plant with
a pink flower. Both white and red are incompletely dominant.
Ticket Out the Door
A) If feather color in a species of birds in codominant, cross a white bird with a black and white spotted bird. List all possible phenotypes.
B) If fur color is incompletely dominant, cross a gray fur dog with a black dog. List all possible phenotypes.
Flashcard Warm-up
Sex chromosomes
For humans, the last set of chromosomes are the sex
chromosomes that determine the gender. Females have two X
chromosomes and males have one X and one Y. Examples of sex-linked traits are colorblindness and hemophilia, these
traits are carried on the X chromosome.
Polygenic trait
trait determined by many genes, results in a wide range of
phenotypesExamples include height, skin color,
hair color
Multiple Alleles: more than two alleles exist for a trait
Blood Type: Phenotype: Type A, AB, B, OGenotype: IAIA or IAi
IAIB IBIB or IBi
ii
Blood donation
clotting clotting
clotting clotting
clotting clotting clotting
Blood Type ExampleCross a heterozygous type A
mom with a Type O dad. What is the chance they have a child with Type O blood?
Sex Linked: trait found on the X sex chromosome
Phenotype: Female – less likely but can show a sex-linked trait
Genotype: XA XA, XA Xa , XaXa Phenotype: Male – sex-linked
traits show up more because they have XY sex chromosomes,
Genotype: XA Y, XaY No male carriers for a sex-linked trait
Sex-linked ExampleCross a colorblind dad with a
mom who is a carrier. What is the chance of this couple having a son who is not colorblind?
PolygeneticTraits that depend on many genes
and create a range of phenotypes.
Ex. Height, skin colorNO PUNNETT SQUARE!
Human skin colorAaBbCc x AaBbCc
◦can produce a wide range of shades
◦most children = intermediate skin color
◦some can be very light & very dark
Nature vs. Nurture:
Nature is heredity – your DNANurture is your environmentThe debate: Which has a greater
influence?Example: We use identical twins
to study the effects of the environment on genes.
Ticket Out the Door1. A sex-linked trait is found on
the __ chromosome.2. Cross a mom with type AB
blood with a dad who is type O. List all possible phenotypes.