2.5 Genetic variation and change

Question 1

multiple alleles

Answer 1

a gene that has more than two alleles

Question 2

linked genes

Answer 2

genes found on the same chromosome. linkage increases the closer they are are and ones close together are more likely to be in the same gamete

Question 3

homozygous

Answer 3

an organism which has two alleles that are the same (BB)

Question 4

heterozygous

Answer 4

an organism which has two alleles that are different (Bb)

Question 5

genotype

Answer 5

the genetic makeup of an organism

Question 6

phenotype

Answer 6

the physical expression of a gene

Question 7

allele

Answer 7

a variant of a gene which is inherited

Question 8

lethal alleles

Answer 8

alleles that produce a phenotypic effect causing the death of an organism. it is caused by the mutation of an essential gene - causing an essential protein to no longer be produced functionally. if heterozygous, the organism will be a carrier (and most likely survive)

Question 9

incomplete dominance

Answer 9

alleles which are mixed in expression ex. blue + yellow = green

Question 10

co-dominance

Answer 10

when two alleles are identically dominant and are thus expressed equally
ex. blue + yellow = blue + yellow

Question 11

monohybrid cross

Answer 11

a cross (punnet square) that involves only one gene
ex. eye colour

Question 12

dihybrid cross

Answer 12

a cross (punnet square) that involves two different genes being inherited
ex. eye and hair colour

Question 13

fillal

Answer 13

relating to an organisms child (the equivalent of “paternal” but for offspring)

Question 14

pedigree chart

Answer 14

family trees showing the presence/absence of a trait

Question 15

test cross

Answer 15

breeding an organism with an unknown genotype with one that is homozygous recessive

Question 16

mutation

Answer 16

a permanent change to the DNA base sequence, it is the only way new alleles are made

Question 17

mutagens

Answer 17

environmental factors, such as UV light, which increases the likelihood of mutations

Question 18

neutral mutation

Answer 18

a mutation with neither positive or negative impacts

Question 19

silent mutation

Answer 19

no observable impact, usually because amino acid has not changed

Question 20

block mutation

Answer 20

changes to a segment of chromosome (could be several genes)
includes inversion, deletion, duplication and translocation

Question 21

inversion mutation

Answer 21

where sections of DNA swap places

Question 22

deletion mutation

Answer 22

where a section of DNA is removed

Question 23

duplication mutation

Answer 23

where a section of DNA is repeated

Question 24

translocation mutation

Answer 24

where a section of DNA is added from another chromosome

Question 25

stop codon

Answer 25

a specific sequence which tells the ribosomes to stop making proteins. mutations can cause a stop codon to be made prematurely, leading the rest of the DNA “code” to be lost OR prolong the stop codon

Question 26

point mutation

Answer 26

a small number of base pair changes

Question 27

homologous chromosomes

Answer 27

two chromosomes that share the same structural features, such as size, banding pattern and centromere position. they also have the same genes at a specific loci position. one chromosome in each pair is from a parent

Question 28

DNA

Answer 28

DNA is a polymer made of “deoxyribose” a nucleotide monomer. in eukaryotes, the DNA supercoils around a histone protein

Question 29

non-favourable alleles

Answer 29

alleles that will be lost from the population because individuals possessing them will have reduced reproduction and survival

Question 30

genetic drift

Answer 30

the change in allele frequency in a population due to chance events

Question 31

genetic biodiversity

Answer 31

the range of all the alleles present in the gene pool. important to the survival of a species because the greater the range of alleles, the greater the variation within the population

Question 32

favourable alleles

Answer 32

will be passed on to offspring

Question 33

selection pressure

Answer 33

a biotic or abiotic factor which effects the survival of an organism and therefore influences reproductive success in a population. some members of the population will not survive and reproduce and thus will not pass on their genes into the next generation

Question 34

template strand

Answer 34

the sequence of DNA that is used during the synthesis of mRNA

Question 35

coding strand

Answer 35

the opposite strand directly corresponding to the mRNA sequence

Question 36

tRNA

Answer 36

brings in the amino acids