7 Genetics... : 17 Inherited Change

Question 1

What is the genotype?

Definition

Answer 1

The genetic constitution of an organism.

Question 2

What is the phenotype?

Definition

Answer 2

The expression of the genetic constitution and its interaction with the environment.

Question 3

What types of alleles are there?

Regarding how they present in the phenotype.

Answer 3

Dominant, recessive, codominant.
There may be many alleles of a single gene.

Question 4

In a diploid organism, what may the alleles at a specific locus be?

What combinations are there?

Answer 4

Homozygous or heterozygous.

Question 5

What is monohybrid inheritance?

Answer 5

The inheritance of a characteristic controlled by a single gene.

Question 6

What ratio from a Punnet square do you expect with monohybrid inheritance?

Answer 6

3 (dominant):1(recessive)

Question 7

What is the law of segregation?

Answer 7

In diploid organisms, characteristics are determined by alleles that occur in pairs. Therefore, only one of each pair of alleles can be present in a single gamete.

Question 8

What is dihybrid inheritance?

Definition

Answer 8

The inheritance of two characteristics determined by two different genes located on different chromosomes.

Question 9

What ratio from a Punnet square do you expect from dihybrid inheritance?

Answer 9

9:3:3:1

Question 10

What is the law of independent assortment?

Answer 10

Each member of a pair of alleles may combine randomly with either of another pair.

Question 11

What is codominance?

Definition

Answer 11

Both alleles are expressed in the phenotype.

Question 12

What ratio from a Punnet square would you expect from codominance?

Answer 12

No definite answer, maybe 1:2:1.
But if the ratio isn’t 3:1 or 9:3:3:1, consider codominance.

Question 13

What are multiple alleles?

Definition

Answer 13

When there are more than two alleles of the same gene.

Question 14

Which type of antibody do each of the blood groups form?

Answer 14

A - forms anti-B antibodies.
B - forms anti-A antibodies.
AB - forms neither antibodies.
O - forms both antibodies.

Question 15

Which type of antigen do each of the blood groups produce?

Answer 15

I^A - antigen A.
I^B - antigen B.
I^O - neither antigen.

Question 16

What is a sex-linked characteristic?

Answer 16

When the allele that codes for it is located on a sex chromosome.

Question 17

Why are males more likely to express recessive phenotypes for sex-linked genes?

Answer 17

The Y chromosome is shorter so carries fewer genes. Most genes on the sex chromosomes are carried by the X chromosome (X-linked genes).
Males only have one X chromosome so only carry one allele for sex-linked genes. Therefore they express the characteristic if the allele is recessive.

They only need to inherit one recessive X allele to express it.

Question 18

What are autosomal chromosomes?

Answer 18

Chromosomes that aren’t sex chromosomes.

Question 19

Why are autosomal genes linked?

Answer 19

Genes on the same autosome are linked.
Because they’re on the same autosome, they’ll stay together during independent segregation of chromosomes and their alleles will be passed on to offspring together. (assuming crossing-over doesn’t split them up).

Question 20

What does it mean if two genes on an autosome are closer together?

Answer 20

They are more closely linked because crossing over is less likely to split them up.

Question 21

What ratio from a Punnet square would you expect with autosomal linkage?

Answer 21

Because the two autosomally-linked alleles are inherited together, there’s a higher proportion of offspring that injerit their parents’ heterozygous genotype.
Therefore, the phenotypic ratio will be different from expected.
e.g. a dihybrid cross would probably end up with 9:3:3:1 but with autosomally-linked alleles, the ratio could be more like 3:1.

Question 22

What is epistasis?

Definition

Answer 22

The allele of one gene masks the expression of the alleles of other genes.

Question 23

What is likely to be the phenotypic ratio in a dihybrid cross involving a recessive epistatic allele?

Answer 23

9:3:4

Question 24

What is likely to be the phenotypic ratio in a dihybrid cross involving a dominant epistatic allele?

Answer 24

12:3:1

Question 25

What is the chi-squared test used for?

Answer 25

To see if the results of an experiment support a theory.

Question 26

What is the null hypothesis for any experiment?

Answer 26

There is no significant difference between the observed and expected results (with context).

Question 27

What does it mean if your x^2 value is larger than or equal to the critical value?

Answer 27

There is a significant difference between the observed and expected results. Reject the null hypothesis.

Question 28

What does it mean if your x^2 value is smaller than the critical value?

Answer 28

There is no significant difference between the observed and expected results. Cannot reject null hypothesis.

Question 29

How do you work out the degrees of freedom in a chi-squared test?

Answer 29

Number of classes - 1

Question 30

When can the chi-squared test be used?

Answer 30

When the sample size is relatively large, the data falls into discrete categories, and there are only raw counts of data.

Question 31

What is monohybrid inheritance represented as in a punnet square?

What are the alleles represented by?

Answer 31

e.g. Rr, rr, RR

Question 32

What is dihybrid inheritance represented as in a punnet square?

What are the alleles represented by?

Answer 32

e.g. RRYY, rryy, RrYy

Question 33

What is codominance represented as in a punnet square?

What are the alleles represented as?

Answer 33

e.g. H^NH^N