Chapter 17 - Inheritence

Question 1

What is meant by diploid

Answer 1

An organism with a pair of homologous chromosomes, it has 2 alleles of each gene

Question 2

What is a gene

Answer 2

A sequence of DNA that codes for a protein

Question 3

What is an allele

Answer 3

A variation or version of a gene eg A B O blood

Question 4

What is a genotype

Answer 4

The combination of alleles an organism has

Question 5

What is a phenotype

Answer 5

The physical expression of the genotype and it’s interaction with the environment

Question 6

What is a dominant allele

Answer 6

An allele always expressed in the phenotype when present

Question 7

What is a recessive allele

Answer 7

An allele only expressed when homozygous

Question 8

What are codominant alleles

Answer 8

When both alleles are expressed in the phenotype, phenotype is intermediate

Question 9

What is homozygous

Answer 9

When both alleles are the same

Question 10

What is heterozygous

Answer 10

When alleles are not the same

Question 11

What is the locus

Answer 11

The location or position of a gene on a chromosome

Alleles of a gene always have the same locus

Question 12

What is mono hybrid inheritance

Answer 12

When inheritance of a characteristic is controlled by a single gene

Question 13

What is dihybrid inheritance

Answer 13

Inheritance of 2 characteristics that are controlled by separate genes

Question 14

What is the expected phenotypic ratio for F2 generation in dihybrid inheritance

Answer 14

9:3:3:1

Question 16

What is an example of codominant alleles

Answer 16

A and B blood groups are codominant

o is recessive so not part of it

Question 17

How is blood groups represented on a punnet square

Answer 17

Capital I to the power of whatever the blood group is

Eg I^B

Question 18

What phenotypic ratios does a dihybrid cross on epistaxis genes cause

Answer 18

Recessive epistatic allele = 9:3:4

Dominant epistatic allele = 12:3:1

Question 19

What is meant by an autosome

Answer 19

Non-sex chromosomes

Question 20

How many autosomes does a human have

Answer 20

44

Question 21

Describe autosomal linkage

Answer 21

• Genes on the same autosome are linked (the closer the lock of autosomes the more closely linked they are)
• They will stay together during independent segregation
• They will be inherited together
• Effects the expected phenotypic ratio of 9:3:3:1
• Because linked genes are inherited together they behave more like a mono hybrid cross 3:1
• Autosomal linkage means that more offspring will have the same genotype and phenotype as their parents

Question 22

Why may autosomal linkage not result in more offspring having the same genotype and phenotype as their parents

Answer 22

• Alleles May be separated during crossing over

Question 23

What is meant by a homologous pair

Answer 23

The pair of chromosomes a diploid organism has, one from mother and one from father
They are the same genes but different alleles

Question 24

What is meant by sex linkage

Answer 24

The expression of alleles located on sex chromosomes depends on the sex of the individual

Question 25

What are the sex chromosomes of females and males

Answer 25

Females XX
Males XY
Y is missing many genes present on X

Question 26

Explain how haemophilia is much more common in men than women

Answer 26

X^H X^h Y

• Females have 2 X chromosomes, so must be homozygous to suffer
• Males only have one X chromosome, if it is recessive they will suffer
• Draw this out (in folder)

Question 27

What is meant by epistasis

Answer 27

An interaction between genes when the expression of one gene suppressed the expression of another gene
Or
When a phenotype is controlled by more than one gene