10.2 Inheritance

Question 1

What is segregation?

Answer 1

The alleles of the same gene separating during meiosis.

Question 2

What is independent assortment?

Answer 2

Different genes located on different chromosomes move independently from each other.

Question 3

What genes are unlinked?

Answer 3

Found on different chromosomes and segregate independently as a result of meiosis.

Question 4

What genes are linked?

Answer 4

On the same chromosome and do not segregate independently.

Question 5

What is an exception for linked genes that are far apart on chromosomes?

Answer 5

Crossing over between genes occurs frequently causing separation of genes, making it seem like they’re unlinked.

Question 6

What is a dihybrid cross?

Answer 6

The inheritance of two genes is investigated together. Founded by Mendel.

Question 7

What was the exception to Mendel’s rule?

Answer 7

Discovered by Thomas Morgan with experiment with the fruit fly. Believed that variations seen in organisms is explained by environmental influence.

Question 8

How did Thomas Morgan discover non-Mendelian ratios.

Answer 8

He bred thousands of fruit flies. Notice one fruit fly with abnormal white eyes instead of normal red eyes.
- He mated the white-eyed fruit fly with a red-eyed fly.
- F1: Most of the offspring were red-eyed with minimal white-eyed flies.
- F2: White-eyed flies appeared in larger numbers.

Question 9

What is the gene locus?

Answer 9

Each particular gene is found in a specific position on one chromosome type.

Question 10

What is homologous genes?

Answer 10

When two chromosomes have the same sequence of genes. Not identical because some alleles can differ.

Question 11

What is an autosome?

Answer 11

Any chromosome that is not a sex chromosome (in humans, number 1-22).

Question 12

What is a sex chromosome?

Answer 12

A chromosome involved with determining the sex of an organism (in humans, X and Y).

Question 13

How many autosomes to diploid nuclei have?

Answer 13

They have two of each type of autosome.

Question 14

What are the two types of linkage?

Answer 14

Autosomal gene linkage and Sex Linkage.

Question 15

What is autosomal gene linkage?

Answer 15

When the genes are on the same autosome.

Question 16

What is sex linkage?

Answer 16

When the genes are located on the X chromosome.

Question 17

What makes genes linked?

Answer 17

Genes that do not independently assort because they’re located near each other on the same chromosome. The genes travel together during meiosis and alleles end up on the same gamete.

Question 18

What is variation?

Answer 18

Differences between individual organisms. When individuals fall into a number of distinct categories, variation is discrete or continuous.

Question 19

What is discrete variation?

Answer 19

Individuals fall into a distinct category. There isn’t a continuous range, you either “are or are not”.

Question 20

What is continuous variation?

Answer 20

There is a range of measurements from one extreme to the other. Due to polygenic (combined effect of many genes) and often influenced by environment.

Question 21

What is an example of discrete variations?

Answer 21

Blood types: there are several and no in-between category.

Question 22

What is an additive effect?

Answer 22

Examples of inheritance in which two or more genes affect the same character.

Question 23

What is a polygenic characteristic?

Answer 23

Characteristics determined by many genes. Each gene has an additive effect on the overall phenotype.

Question 24

What is an example of polygenic inheritance?

Answer 24

Two gene cross with codominant alleles.

Question 25

What is recombination frequency?

Answer 25

We can see if two genes are linked, and how tightly, by using data from genetic crosses.

Question 26

How do you make a linkage map?

Answer 26

By finding recombination frequencies for many gene pairs, we can make linkage maps that show the order and relative distances of the genes on the chromosome.

Question 27

What is polygenic inheritance?

Answer 27

When there are more than two pairs of alleles located at different gene locus that results in an increased number of possible genotypes. Increases the number of genes involved and possible genotypes.

Question 28

What is continuous variation?

Answer 28

The increase in genotypes causes an increase in phenotypes until it becomes impossible to differentiate between the groups.