10.2 Inheritance

Question 1

How do unlinked genes segregate as a result of meiosis?

Answer 1

Unlinked genes segregate independently as a result of meiosis

Question 2

What is segregation?

Answer 2

The separation of the two alleles of every gene that occurs during meiosis

Question 3

What is independent assortment?

Answer 3

The observation that the alleles of one gene segregate independently of the alleles of other genes

Question 4

Where can unlinked genes be found?

Answer 4

On different chromosomes

Question 5

How do unlinked genes segregate?

Answer 5

Independently as a result of meiosis

Question 6

Where can linked genes be found?

Answer 6

On the same chromosome

Question 7

How do linked genes segregate?

Answer 7

They do not segregate independently

Question 8

What is the exception for linked genes to be segregated independently?

Answer 8

If they are far apart on the chromosome

Question 9

What does it mean when two gene loci are further apart on a chromosome?

Answer 9

There is a greater chance of recmobinant gametes forming

Question 10

When are gene loci said to be linked?

Answer 10

If they are on the same chromosome

Question 11

What is a locus of a gene?

Answer 11

A particular gene that is found in a specific position on one chromosome type

Question 12

What does it mean when two chromosomes are homologous?

Answer 12

They have the same sequence of genes

Question 13

How are homologous chromosomes not usually identitical to each other?

Answer 13

Because, for at least some of the genes on them, the alleles will be different

Question 14

What are autosomes?

Answer 14

Chromosomes that are common to males and females
* In males there is an X and another is a Y chromosome.
* In female two of them are X chromosomes
* The other 6 chromosomes are common to both male and females <- they are called autosomes

Question 15

What are autosomes?

Answer 15

Chromosomes that are common to males and females
* In males there is an X and another is a Y chromosome.
* In female two of them are X chromosomes
* The other 6 chromosomes are common to both male and females <- they are called autosomes

Question 16

What are the two types of linkage?

Answer 16

• Autosomal gene linkage
• Sex linkage

Question 17

What is autosomal linkage?

Answer 17

When the genes are on the same autosome
* gene loci present on the same autosome (non-sex chromosome) that are often inherited together

Question 18

What is sex linkage?

Answer 18

When the genes are located on the X chromosome

Question 19

What can variation be? (2)

Answer 19

Discrete or continuous

Question 20

What is referred to as variation?

Answer 20

The differences between individual organisms

Question 21

Is blood type discrete or continuous variation?

Answer 21

Discrete because while there are several blood types, there are no in-between categories

Question 22

Is blood type discrete or continuous variation?

Answer 22

Discrete because while there are several blood types, there are no in-between categories

Question 23

What type of variation do the phenotypes of polygenic characteristics tend to show?

Answer 23

Continuous variation

Question 24

What is an example of continuous variation?

Answer 24

Height

Question 25

What does a normal distrubution curve look like?

Answer 25

A bell-shaped curve

Question 26

What are 4 characteristics of a normal distribution?

Answer 26

* The mean, mode and median are the same * The distribution has a characteristic bell shape which is symmetrical about the mean * 50% of the values are less than the mean and 50% are greater than the mean * Most values lie close to the mean value - the number of individuals at the extremes are low

Question 27

What are polygenic traits?

Answer 27

Traits that are controlled by two or more than two genes (usually by many different genes) at different loci on different chromosomes * These genes are described as polygenes

Question 28

What is polygenic inheritance?

Answer 28

Polygenic inheritance refers to a single characteristic that is controlled by more than two genes (also called multifactorial inheritance) Polygenic inheritance patterns normally follow a normal (bell-shaped) distribution curve - it shows continuous variation.

Question 29

What are the two causes of variation?

Answer 29

Genetic and environmental

Question 30

What are 3 causes of genetic variation?

Answer 30

* Mutations - changes to the DNA sequence that lead to new alleles * Meiosis - independent assortment and crossing over * Sexual reproduction - random fusion of gametes from two unrelated individuals

Question 31

What are characteristics that exhibit discontinuous variation usually determined by?

Answer 31

the alleles of a single gene locus - they are monogenic

Question 32

What is meant by monogenic?

Answer 32

Characteristics that exhibit discontinuous variation that are determined by the alles of a single gene locus * One gene = monogenic

Question 33

What is meant by polygenic?

Answer 33

When many genes are involved in determining such characteristics

Question 34

What does it mean when the alleles have an additive effect on the phenotype?

Answer 34

The alleles of each gene may contribute a small amount to the phenotype, therefore the alleles have an additive effect on the phenotype

Question 35

How does polygenic characteristics show continuous variation?

Answer 35

As a result of the additive effect on the phenotype, the phenotypic categories vary in a quantitive way. * The greater number of gene loci contributing to the determination of the characteristic, the more continuous the variation (the greater the range)

Question 36

Contintious vs discontinous variation (discrete)

Answer 36

Question 37

How can the number and frequency of variants be predicted?

Answer 37

Using alternative rows of Pascal's triangle

Question 38

What may polygenic traits also be influenced by besides by multiple genes?

Answer 38

Environmental factors

Question 39

What is variation due to polygenic inheritance tend to be?

Answer 39

continuous

Question 40

What is an example of continious variation in humans?

Answer 40

Skin color * Due to the influence of several genes * Partially due to the environment - sunlight stimulates the production of the black pigment melanin in the skin

Question 41

How is skin color an example of polygenic inheritance?

Answer 41

It is due to the influence of several genes

Question 42

What is recombination?

Answer 42

The formation of a chromosome or DNA with a new combination of alleles

Question 43

What is a recombinant?

Answer 43

An individual that has this recombinant chromosome and therefore has a different combination of characters from either of the original parents is called a recombinant