Chapter Twelve

Question 1

What are genes?

Answer 1

They are segments of DNA that encode info that are used to build specific proteins.

Question 2

What is an allele?

Answer 2

they are alternate forms of a gene

example is R and r, which are the same gene but just different forms

Question 3

Who is the father of genetics?

Answer 3

Gregor Mendel
worked with garden peas to study heredity

Question 4

what is phenotype?

Answer 4

the actual physical appearance of a organism

Question 5

what is genotype?

Answer 5

the genetic constitution of an organism

Question 6

What is a dominant allele?

Answer 6

it is an alternate form of a gene that is expressed, and their effects are exerted when they are present

they code for functional proteins

Question 7

What is a recessive allele?

Answer 7

it is an alternate form of a gene that isn’t expressed when the dominant allele is present.

they code for non functional proteins

Question 8

What does homozygous mean?

Answer 8

when the two alleles (one from mom and one from dad) are the same HH or hh

Question 9

What does heterozygous mean?

Answer 9

when the two alleles are different, one dominant and recessive Hh

Question 10

Explain the (P), (F1), and (F2) generations in Mendel’s original round and wrinkled seeds.

Answer 10

P generation started with a dominant homozygous and a recessive homozygous

F1 the resulting offspring of P is all heterozygous, which are self-bred

F2 the result of two heterozygotes gives the 3 to 1 phenotypic ratio of and the 1 to 2 to 1 genotypic ratio

Question 11

Explain the P, F1 and F2 in the dihybrid cross of seed shape and color.

Answer 11

P in this scenario was the homozygous dominant RRYY and the homozygous recessive rryy

F1 resulting from P was all heterozygotes RrYy\

F2 shows a 9:3:3:1 phenotypic ratio, but 9 different genotypes show in a 16 punnet square in which the RY, Ry, rY, and ry are bred

Question 12

What was the significance of Mendel’s first law?

Answer 12

that our genes occur in pairs and segregate from each other during formation of gametes

the law of segregation entails that two copies of a gene separate during gamete formation (one copy per sex cell)

Question 13

What was Mendel’s second law?

Answer 13

the law of independent assortment which states that copies of different genes on the gametes assort independently shown by the dihybrid cross

Question 14

Who do offspring inherit their alleles from?

Answer 14

they inherit them one from each parent and they are either heterozygous or homozygous

Question 15

How should the genotype of a father (HhBb) be represented on a punnett square?

Answer 15

father should be on top and the four gametes should be HB, Hb, hB, hb

Question 16

How should the genotype of a mother HHbb be represented on a punnett square?

Answer 16

mother should be on the side and the four gametes should be Hb, Hb, Hb, Hb

Question 17

What is the multiplication rule?

Answer 17

the probability of two independent events happening TOGETHER can be found by multiplying the probabilities of the events together

eg. getting a heads two times flipping coins is a 1/4 odds (1/2 x 1/2)

Question 18

What is the addition rule?

Answer 18

the probability that an event can occur in two different ways is just the sum of the separate probabilities

eg. chances of getting a heads OR a tails in one turn (1/2 + 1/2) = 1

Question 19

What is true breeding?

Answer 19

when the parental generation has the same exact genotype in order to show the same phenotype in the next generation

e.g would be HH with another HH or yy with yy

Question 20

What is incomplete dominance?

Answer 20

when alleles are neither dominant or recessive, so heterozygotes have a new intermediate phenotype,

alleles have not blended and the original phenotypes will show up later down the road

MORE PHENOTYPIC DIVERSITY

Question 21

what is co-dominance?

Answer 21

when more than one allele codes for a functional protein,

dominant R red allele and dominant W white allele come together to have red and white spots or vice versa

Question 22

What is wild type?

Answer 22

it is the allele present in most of the population.

Question 23

What is a mutation?

Answer 23

it is a stable inherited change in genetic material

-alleles that are not wild types are mutant alleles.

Question 24

Where do both wild type and mutant type alleles reside?

Answer 24

the same locus

Question 25

What is a locus?

Answer 25

it is the specific location of a gene on a chromosome

Question 26

What are linked genes?

Answer 26

since many genes are found on a single chromosome, when genes are physically linked they reveal inheritance patterns that aren’t mendelian

example is the fruit flies where color of bodies and size wings were linked genes and so the recessive pairs and dominant pairs showed a different ratio than the 1 to 1 to 1 to 1 predicted

Question 27

What is Pleiotropic?

Answer 27

is when one allele has multiple phenotypic effects

example would be Marfan syndrome, which is caused by variation in the FBN1 gene, people with Marfan syndrome tend to be tall with long thin fingers, toes and limbs.

Question 28

What is epistasis?

Answer 28

is when the phenotypic expression of one gene is influenced by another gene

example is that alleles for black and brown dogs aren’t expressed unless the E allele is expressed bbEe and BbEE are brown and black dogs respectively

Question 29

What is the effect of the environment on phenotype?

Answer 29

Light, temperature, nutrition, etc. effect the expression of genotype

Question 30

What is significant about Siamese cats and rabbits in reference to environmental effect ?

Answer 30

There is point restriction coat patterns in them where enzymes that produce dark fur are inactive at higher temps

therefore the nose ears are cooler so they appear darker

Question 31

How can prokaryotes exchange genes?

Answer 31

they exchange genes when the DNA of a donor cell passes to recipient cell through conjugation

DNA often lines up and crossing over occurs, changing the makeup.

Question 32

What are plasmids?

Answer 32

they are small circular chromosomes that can
1. move between cells during DNA transfer
2. can replicate independently of main chromosome

Question 33

What kind of genes do plasmids contain?

Answer 33

1. genes that code for unusual metabolic functions, like breaking down hydrocarbons
2. genes that code for antibiotic resistance
3. genes that code for making a sex pilus