A3 - Genes, Alleles + Inheritance

Question 1

Define gene

Accepted Answer

Section of DNA that codes for a protein of functional RNA

Question 2

Define locus

Accepted Answer

Position of an allele on a chromosome

Question 3

Define genotype

Accepted Answer

All alleles in an organism Only altered by mutation

Question 4

Define phenotype

Accepted Answer

Observable characteristics of an organism Genotype + environment

Question 5

Define allele

Accepted Answer

Different versions of the same gene

Question 6

Define homozygous

Accepted Answer

Same alleles at a particular gene locus on homologous chromosomes

Question 7

Define heterozygous

Accepted Answer

Different alleles at a particular gene locus on homologous chromosomes

Question 8

Define dominant

Accepted Answer

Only 1 of these alleles needed to be expressed

Question 9

Define recessive

Accepted Answer

2 identical alleles needed for it to be expressed

Question 10

Define codominance

Accepted Answer

Both heterozygous alleles are equally expressed

Question 11

Define multiple alleles

Accepted Answer

More than 2 alleles available at a locus

Question 12

Define sex-linked traits

Accepted Answer

Traits on x chromosome Females need 2 copies of recessive allele for expression Males only need 1

Question 13

Define epistasis

Accepted Answer

For some genes to be seen other genes need to be expressed Eg. black stripes only in phenotype if coat colour isn't also black

Question 14

Define autosomal linkage

Accepted Answer

Genes close together on same chromosome tend to be inherited together Further apart = more likely to be separated in crossing over and ercombination

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