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A-Level Biology > 6.1.2 Genetic inheritance > Flashcards

6.1.2 Genetic inheritance Flashcards

(48 cards)

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1
Q

monogenic definition

A

determined by a single gene

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2
Q

gene locus definition

A

position of gene on a chromosome

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3
Q

heterozygous definition

A

having different alleles for the same gene locus on a pair of homologous chromosome

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4
Q

homozygous definition

A

having same alleles at the same gene locus on a pair of homologous chromosomes

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5
Q

true-bred definition

A

homozygous

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6
Q

dominant definition

A

masks the effects of recessive alleles

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7
Q

recessive definition

A

masked by dominant alleles

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8
Q

F1 definition

A

first generation of offspring (to original parents)

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9
Q

F2 definition

A

second generation (offspring of F1)

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10
Q

continuous variation features

A

no defined categories
there is a range (any value is possible)
caused by more than one gene and often environment
greater number of gene loci contributing to characteristic, greater range in variation
quantitative

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11
Q

discontinuous variation features

A

discrete categories with no intermediates
usually caused by one gene
genes at different loci may interact to influence one characteristic and cause discontinuous variation
no/very little environmental effects cause it
qualitative

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12
Q

polygenic definition

A

caused by more than one gene

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13
Q

epistasis definition

A

expression of one gene is affected by expression of one or more independently inherited genes

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14
Q

environmental factors that influence variation

A

diet in animals leads to changes in mass (malnutrition)
language
scars
plants grown in too little light experience etiolation (rapidly growing stems, weakened cell walls, chlorosis)

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15
Q

chlorosis definition

A

lack of chlorophyll

the environmental factors prevent the expression of genes for chlorophyll production

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16
Q

different blood groups phenotypes

A

A
B
AB
O

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17
Q

sex linkage definition

A

when a gene is present on one of the sex chromosomes

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18
Q

why sex chromosomes are not fully homologous and its impact

A

Y chromosome lacks many genes that code for characteristics on X chromosome
men can neither be homozygous nor heterozygous for these genes
men more likely to have genetic diseases linked to genes on these chromosomes

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19
Q

Haemophilia in genes

A

found on X chromosome but not Y

functional:faulty allele = X^H:X^h

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20
Q

colour blindess

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A

gene causing red-green colour blindness
found on X but not on Y chromosomes
functional/faulty allele: X^B/X^b

21
Q

autosome definition

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A

non-sex genes

22
Q

autosomal linkage definition

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A

linkage when 2 or more genes on the same chromosome are inherited together (they dont undergo independent assortment in metaphase 1)

23
Q

epistasis definition

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A

interaction of non-linked genes (on different chromosomes) where one masks the expression of the other

24
Q

epistasis effect on number of phenotypes

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A

epistasis reduces number of phenotypes in F2 generation and reduced variation

25
epistatic alleles definition
alleles masking the effect of the alleles on the other gene
26
hypostatic alleles definition
alleles whose effect is being masked
27
recessive epistasis definition
when homozygous recessive alleles of gene locus 1 are epistatic to both alleles on gene locus 2 (hypostatic) 9:3:4 ratio
28
dominant epistasis definition
where dominant alleles of gene locus 1 are epistatic to both alleles on gene locus 2 (hypostatic) 12:3:1 or 13:3 ratio
29
epistasis by complementary gene action definition
when 2 different genes work together to express phenotypes | 9:7 or 9:3:4 phenotypic ratio
30
what a non 9:3:3:1 phenotypic ratio means for 4 phenotypes for 2 genes/traits
autosomal linked and crossing over will have occurred further apart the gene loci for linked genes, the more likely crossing over is and higher the number of recombinant phenotypes
31
natural selection/evolution method
V: individuals of a population of same species have different characteristics due to genetic variation O: overproduction of offspring S: selection pressure kills individuals with less advantageous characteristics die S: those with more advantageous characteristics survive AR: those who survive are more likely to reproduce and advantageous alleles are passed onto their offspring
32
Hardy Weinberg assumptions
``` large population no genetic drift random mating no natural selection no mutation no migration ```
33
2 types of natural selection
stabilising selection | directional selection
34
stabilising selection features
occurs when organisms’ environment doesn’t change favours intermediate phenotype (over extremes) reduces variation in a population (e.g. those with short/long fur in constant temperatures selected against, mid length fur will survive, higher frequency of alleles for mid length fur)
35
directional selection features
``` occurs when environment changes favours new (extreme) phenotype causes change in population’s mean phenotype ```
36
genetic drift definition
random changes in alleles frequency in small populations
37
genetic drift features
only small populations as each individual forms a larger proportion of gene pool and greater effect on gene pool not due to natural selection, chance only population alleles can drift from original, could lose alleles from gene pool
38
2 types of genetic drift
genetic bottleneck | founder effect
39
genetic bottleneck features
an event reduces numbers of a population some alleles lost from population at random genetic variation reduced -> genetic drift
40
founder effect features
small number of individuals from an original larger population establish a new population some alleles lost from population at random (these could be advantageous) genetic variation reduced -> genetic drift
41
speciation definition
splitting of a population of a species into 2 isolated population that overtime undergo genetic changes, resulting in reproductive isolation and the formation of 2 different species
42
allopatric speciation mechanism
populations are physically separated e.g. by water/mountains/fences barrier prevents gene flow between populations genetic changes occur in species (caused by genetic drift, mutations or natural selection (different pressures in different areas)) populations become so genetically different they can no longer interbreed (reproductively isolated) new species has been formed
43
sympathetic speciation mechanism
several things can lead to individuals in a population become reproductively isolated: • behavioural changes (sleep patterns, courtship behaviours) • biological changes (size differences, genitalia differences) • genetic changes (change in chromosome number, prevents zygote viability) populations can no longer interbreed to produce fertile offspring, new species been formed
44
artificial selection definition
selective breeding of organisms in order to produce desired phenotypes in an organism (often to benefit to humans) humans choose parents with desired phenotypes and therefore desired alleles and interbreed them to produce offspring with higher frequency of these phenotypes, repeated over many generatjons
45
stages of artificial selection
male and female with desired characteristic chosen and bred together some of the offspring will carry all of the desired characteristics of the mother and father choose the offspring with the all of the desired characteristics and breed together repeat
46
inbreeding features
genetic diversity decreases with each generation, individuals become more and more related likelihood of unintentionally selecting 2 copies of a harmful recessive allele increases in small gene loci …
47
hybrid vigour definition
outcross individuals belonging to 2 different varieties to obtain individuals heterozygous at many gene loci
48
how/when gene has multiple alleles
when it has 3 or more alleles

A-Level Biology (24 decks)

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