How DNA is put together
~DNA: The history of its discovery
~DNA Structure: animated (John Kyrk)
~DNA Models (yes, they're movable)
~DNA Packaging animation
Making proteins during G phase
How does a blueprint of a house become a house? How does
this "code" in a nucleus become flesh and blood??? Here's
Proteins run everything
(see some below). This is when RNA plays its role
with DNA to help produce proteins, a process called
which include the processes of
DNA --> transcription --> RNA --> translation --> PROTEIN
Wiley Biology Basics
Protein Data Bank (PDB.org)
Click on these images of Meiosis I and II to see enlarged version. (source)
When the age of a mother-to-be gets
around 40 or older, notice the probability that Down
Syndrome (and other anomalies) will likely occur with her baby:
here, then click "What is Heredity?"
When gametes combine
Video: How to do a Dihybrid cross
Here For Genetics Problems
TEST ON WEDNESDAY, April 9 (Late start day)
Mutagens: The result of too much radiation
taste PTC paper? Learn more about why humans can or cannot
Here's a good dihybrid, X-linked trait genetics problem. Before you look below at the answer, try to figure out the solution for yourself.
A male that is heterozygous
for type A blood and is a hemophiliac marries a woman who's type AB
and a carrier. What are the
possibilities of genotypes and phenotypes of their offspring?
Genetics Problems (w/answers) (from class)
Monohybrid, Complete Dominance (key)
Create Punnett squares for the following
parentage, and determine
phenotypes/genotypes of offspring:
b. Father: Homozygous for freckles (FF)
M2. Assume brown eyes (B) are dominant to blue (b). A brown-eyed man marries a blue-eyed woman. They have three children, two of whom are brown-eyed and one of whom is blue-eyed. Draw the Punnett square that illustrates this family. What is the man's genotype? What are the genotypes of the children?
M3. In dogs, wire hair (S) is dominant to smooth (s). In a cross of a homozygous wire-haired dog with a smooth-haired dog, what will be the phenotype of the F1 generation?
In rabbits, black fur (B) dominates white
fur (b). Perform the following
crosses. Give phen/gen. for all
Albinism is an inherited recessive condition
in skin color. The absence of the
pigment melanin causes the person to be very
pale with very light hair (a yellowish
white) and pale eye color (cloudy blue).
b. Could any of the normal skin color children eventually pass the albino gene to their children? Which ones?
D1. In Drosophila melanogaster (fruit flies), the gene for dachs (short legs, d) is recessive to the allele for normal leg length (D). The allele for hairy body (h) is recessive to the allele for normal body (H). Determine the genotypes of the F1 for the following crosses:
a. DdHh x DDhh
b. DDHh x Ddhh
c. DdHh x ddhh
In guinea pigs, black hair is dominant to
a. A fully homozygous black, long
In peas, the allele for tall (T) plants
dominate the dwarf allele (t).
a. TtRR x TtRr
Incomplete Dominance / Codominance (key)
IC1. Explain the difference between incomplete dominance and codominance.
In some chickens, the gene for feather color
is controlled by codominance.
The allele for black is B and the allele for
white is W.
If two erminette chickens were crossed,
A black chicken is crossed with a white.
In snapdragons, flower color is controlled
by incomplete dominance.
A pink is crossed with a white.
What cross will produce the most pink
Cross someone with type AB blood with a
heterozygous type A person.
IC9. Mrs. Smith and Mrs. Jones had babies at the same maternity hospital at the same time. Mrs. Smith took home a girl and named her Sue. Mrs. Jones took home a boy and named him Jim. However, Mrs. Jones was sure she had a girl and brought suit against the hospital. Blood tests showed that Mr. Jones had blood type O, Mrs. Jones was type AB. Both Mr. and Mrs. Smith were type B, Sue was type A, and Jim was type O. Had a swap occurred?
In radishes, red and white are
pure-breeding colors, while long and
round are pure-breeding shapes.
The hybrids are purple and oval.
An incomplete dominant gene
controls the color of some chickens:
A second complete dominant gene
controls comp shape;
If a pure-bred black chicken with a
rose comb is mated to a splashed white
chicken with a single comb (P generation),
fraction of the F2 generation
(from an F1 cross) will be blue
with a single comb?
Note: When working with sex linked (or X linked) traits, use the sex chromosome symbols X and y for the alleles in your problems.
Are these statements about sex-linked traits
TRUE or FALSE?
a. A girl cannot have hemophilia unless mom
S2. In colorblindness, the normal male genotype is XCy, whereby the colorblind male genotype is Xcy.
a. What is the genotype of a normal female?
S3. Cross a colorblind male with a carrier. What might their children be?
Can a couple who sees color normally have a
colorblind son? Daughter?
Cross a colorblind male with a perfectly
normal homozygous female.
S5. A hemophiliac male, whose mother and father both had normally clotting blood, marries and has 4 children with a lady who has normally clotting blood, but whose father was a hemophiliac. Can you determine the possible genotypes and phenotypes of all the individuals boldfaced?
MA1. Coat color in rabbits is determined by a single gene that has at least four different alleles. Different combinations of alleles result in four colors: Full color (brown), Chinchilla (gray), Himalayan (black and white), and Albino (white). Using the following information, complete the Punnett squares and answer the questions.
C = full color, dominant to everything else
a. What are the possible genotypes for an
e. C cch x
Human hair color is controlled by one gene
with four alleles
HBr = brown HBd = blonde hR = red hbk = black
So, possible genotypes and phenotypes can be:
HBdHBd or HBdhbk = blonde HBdhR = strawberry blonde
HBdHBr = mousy brown HBrHBr or HBrhbk = brown
HBrhR = auburn hRhR or hRhbk = red hbkhbk = black
If someone with auburn hair has children with someone with red hair (but whose mother had black hair), what are the genotype and phenotype probabilities for their children?
Sex Linked / Dihybrid
SD1. Find out the F1's phenotypes and genotypes.
N - Dominant gene for normal skin color (autosomal)
H - Dominant gene for normal blood clotting
factors (X chrom)
Problem: Cross an albino male bleeder with a normal skinned carrier.
SD2. Colorblindness is a sex linked (X linked) recessive trait.
b. Cross a colorblind male with a female who has normal color vision (but whose father was colorblind). Show the genotypes of all possible children.
c. Can a normal vision male and a normal vision female produce a colorblind son? Can they produce a colorblind daughter?
d. Can a colorblind man and a homozygous normal color vision woman have any colorblind children? Can they produce a carrier?
e. Can a colorblind couple produce any normal visioned children?
Answer for problem above:
THE STEPS TO SOLVING THIS (and ANY) PUNNETT PROBLEM:
1. Step one: Determine the genotypes of the parents (diploid).
The Father: Male, heterozygous for type A blood and hemophiliac = IAi Xhy
The Mother: Female, type AB and a carrier = IAIB XHXh
So, your cross will be:
2. Step two: Determine the possible gametes that each parent could form (haploid):
3. Set up and solve your Punnett
4. Determine the genotypes and phenotypes, and their ratios.
square in the Punnett below exhibits a unique genotype.
Type A carrier female
Images of some proteins:
All have a different shape.
Don't forget: form and function go hand in hand.
They're shaped like they are because of what they do.
You'll recognize 4hhb, 2hiu, 1igt, 1i6h, 1bkv, and others.
(Hint, zoom your screen to 200X to read it better)
Can two medium toned people have a white or black baby?
Because three sets of alleles determine skin color
- yes -
though the chances are 1/64...
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