4.3 - Inheritance

Question 1

Define what an allele is

Answer 1

A version of a gene that occurs at the same locus on homologous chromosomes

Question 2

What is autosomal linkage?

Answer 2

When two or more genes are positioned on the same autosome. They are unlikely to be separated by crossing over during meiosis so are often inherited together

Question 3

Define autosome

Answer 3

A chromosome that is not an X or a Y chromosome

Question 4

Explain what carcinogen is

Answer 4

A type of mutagen that causes cancer

Question 5

What is the Chi-squared test?

Answer 5

A statistical test used to determine whether a pattern of inheritance is statistically significant

Question 6

What is chromosome mutation?

Answer 6

A change in the structure or number of chromosomes. This affects many genes

Question 7

What is co-dominance?

Answer 7

When both alleles for a gene in a heterozygous organism equally contribute to the phenotype

Question 8

What is the degrees of freedom (X2 test)?

Answer 8

The number of categories minus one

Question 9

What is the dihybrid mandelian inheritance?

Answer 9

The determination of a trait by the inheritance of two genes

Question 10

Define the meaning of dominant

Answer 10

Describes an allele that is always expressed. Represented by a capital letter

Question 11

Explain what Down’s syndrome is

Answer 11

A genetic disorder characterised by delayed development and learning disabilities. Due to non-disjunction, an affected individual possesses three copies of chromosome 21

Question 12

What is Duchenne muscular dystrophy (DMD)?

Answer 12

An X-linked recessive condition characterised by muscle degeneration and weakness. It is more common among males because they only inherit one X chromosome.

Question 13

Define what epigenetics are

Answer 13

The study of changes in gene expression that are not due to alterations in the nucleotide base sequence of DNA

Question 14

What is F1 generation?

Answer 14

The first generation of offspring resulting from the cross of two individuals in the parental generation

Question 15

What is F2 generation?

Answer 15

The second generation of offspring resulting from the cross of two individuals in the F1 generation

Question 16

Explain what a gene is

Answer 16

A length of DNA on a chromosome that codes for the production of one or more polypeptide chains and functional RNA

Question 17

What is gene mutation?

Answer 17

A change to at least one nucleotide base in DNA or the arrangement of bases. Gene mutations can occur spontaneously during DNA replication and may be beneficial, damaging or neutral

Question 18

Define what a genotype is

Answer 18

An organism’s genetic composition. Describes all alleles

Question 19

What is haemphilia?

Answer 19

An X-linked recessive condition that results in excessive bleeding and blood that is slow to clot. It is more common among males because they only inherit one X chromosome

Question 20

Define what heterozygous means

Answer 20

When someone has two different alleles of a gene e.g. Ff

Question 21

What is histone modification?

Answer 21

The alteration of histones by the addition of methyl, acetyl, or phosphate groups. This can increase or decrease gene expression by making the DNA more or less accessible to transcription factors

Question 22

Define what homozygous means

Answer 22

When someone has two identical alleles of a gene e.g. ff

Question 23

Explain what locus means

Answer 23

The position of a gene on a chromosome

Question 24

What is methylation?

Answer 24

The transfer of methyl groups to cytosine bases of DNA. Methylation inhibits transcription by making the DNA less accessible to transcription factors or preventing transcription factors from binding. This deactivates the gene

Question 25

What is monohybrid mendalian inheritance?

Answer 25

The determination of a trait by the inheritance of a single gene

Question 26

Define what a mutagen is

Answer 26

A chemical, biological or physical agent that increases the rate of gene mutations above normal level

Question 27

What is non-disjunction?

Answer 27

The failure of homologous chromosomes to separate in anaphase I or sister chromatids to separate in anaphase II, resulting in a change in the diploid number of chromosomes

Question 28

What is oncogene?

Answer 28

Mutations of proto-oncogenes that are activated continuously, resulting in uncontrolled cell division

Question 29

What is a phenotype?

Answer 29

An organism’s observable characteristics. Due to interactions of the genotype and the environment

Question 30

Explain what recessive means

Answer 30

Describes an allele that is only expressed in the absence of a dominant allele. Represented by a small letter

Question 31

What is a sex chromosome?

Answer 31

A chromosome that determines the sex of an organism. e.g X and Y chromosomes in humans and other mammals

Question 32

What does sex-linkage mean?

Answer 32

The inheritance of a gene only present on the X chromosome in organisms with X and Y chromosomes. This is due to many gene loci on the X chromosome having no counterpart on the Y chromosome

Question 33

What is the sickle cell anaemia?

Answer 33

A recessive genetic disorder caused by a substitution mutation on chromosome 11. This results in abnormal haemoglobin which distorts red blood cells