Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biology A Level > Inheritance And Evolution > Flashcards

Inheritance And Evolution Flashcards

(79 cards)

Start Studying
1
Q

Gene

A

A base sequence of DNA that codes for the amino acid sequence of a polypeptide which results inn a characteristic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Allele

A

One or more alternative versions of the same gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Genotype

A

The genetic constitutions of an organism - the different alleles it has

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Phenotype

A

The expression of the genetic constitution and its interaction with the environment - what characteristics an organism has as a result of its genes and the effects of the environment on them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Gene locus

A

The position on a chromosome where a particular gene is found

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Dominant alleles of a gene

A

An allele whose characteristic appears in the phenotype even when there is only one copy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Recessive alleles of a gene

A

An allele whose characteristics only appears in the phenotype if two copies are present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Co dominant alleles of a gene

A

An allele whose characteristics appear together with another allele in the phenotype because neither allele is recessive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Multiple alleles

A

More than two alleles of a gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Diploid

A

A cell with two of each type of chromosome

Homologous pairs of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Haploid

A

A cell with only one of each type of chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Heterozygous genotype

A

Two different alleles at the same gene locus on each of a pair of chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Homozygous genotype

A

Two of the same alleles at the same gene locusts each of a pair of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Monohybrid inheritance

A

The inheritance of a single characteristic controlled b one gene with two or more alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Dihybrid inheritance

A

The inheritance of two characteristics which are controlled by different genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Sex linked characteristic

A

Alleles that code for the characteristics are located on the sex chromosome (X OR Y)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Autosomal chromosomes

A

A chromosome that is not a sex chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Autosomal linkage

A

When two genes coding for different characteristics are located on the same chromosome and consequently are inherited together.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Epistasis

A

When the alleles of one gene mask the expression of alleles on another gene.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Dominant epistasis

A

Just one copy of the epistasis allele will block expression of the second gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Recessive epistasis

A

Two copies of the epistasis allele are required to block expression of the second gene.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Dihybrid crosses with no linkage

A

Inheritance of two different characteristics controlled by two different genes found on two different chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

In meiosis 1 homologous pairs segregate independently this mean that

A

Genes on different chromosomes are inherited independently

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Epistasis

3

A

An allele of one epistasis gene masks (blocks)
The expression of a second gene

One characteristic controlled by two genes

Epistasis can be either recessive epistasis or dominant epistasis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Recessive epistasis
Only a homozygous recessive genotype on the epistatic gene masks the expression of the second gene.
26
Dominant epistasis
Occurs when the epistatic allele is dominant, the organism can be heteros or homozygous to show the effect
27
Mutation
Random changes in base sequences of genes to give new allele
28
Meiosis
Crossing over and independent segregation of homologous pairs
29
Homologous pairs form
Bivalents at the start of meiosis 1
30
Crossing over occurs
Sections of non sister chromatids are exchanged to give new combinations of alleles in the gametes. Chiasma are the points a which the crossing over occurs
31
During meiosis 1
Homologous pairs are separated | The homologous pairs segregate independently giving many combinations of maternal and paternal alleles in the gametes.
32
Random fusion of gametes
Any gamete from one parent is equally likely to fuse with any gamete from the other parent regardless of the allele combinations they contain.
33
Autosomal genes
Yess carries on chromosome 1-22
34
How many genes on X chromosome in humans
Roughly 2000
35
Y chromosome
Much smaller | Carries only 78 genes
36
In males the X chromosome
I inherited from ty mother therefore all males with a recessive sex linked condition must have a mother who is a carrier of the condition (or has the condition)
37
All females receive an X chromosome from
Their father- if he has a recessive sex linked condition then the daughter will be a carrier of the condition (or have the condition)
38
Males have only one
X chromosome and will have a recessive sex linked condition with just one recessive allele
39
Females have two
X chromosomes and will only have a sex linked recessive condition if homozygous for the recessive allele
40
Dihybrid crosses with no linkage
Inheritance of two different characteristics controlled by two different genes found on two different chromosomes
41
In meiosis 1 homologous pairs segregate independently
This means that genes on different chromosomes are inherited independently
42
Epistasis | 3
An allele of one epistatic green masks the expression of a second gene One characteristic controlled by two genes Can either be recessive epistasis or dominant epistasis
43
Linkage
Inheritance of genes located on the same autosomal chromosomes
44
Chi squared test
Statistical test used to compare actual and expected results to determine whether the differences are due to chance or are significant
45
Degrees of freedom
Number of categories - 1
46
Population
A group of organisms of the same species living in a particular place at a particular time, the organisms are free to interbreed with one another
47
Gene pool
The complete range of alleles present in a population
48
Allele frequency
How often an allele occurs in a population expressed as a percentage
49
Genotype frequency
How often a genotype appears in a population expressed as a percentage
50
Hardy-Weinberg model can only be used if allele frequency doesn’t change over time, following conditions must apply 5
Large population- less likely for genetic drift Mating is random One allele does not confer an advantage so that natural selection will not occur There are no emigrants or immigrants No mutations occur
51
Equation for allele frequency
P + q = 1
52
Equation for genotype frequency
P^2 + 2pq + q^2 = 1
53
P
Dominant allele
54
Q
Recessive allele
55
P^2
Homozygous dominant genotype
56
2pq
Heterozygous genotype
57
Q^2
Homozygous recessive genotype
58
Calculating actual allele frequency
When alleles are co dominant and the heterozygous phenotype is distinguishable from the homozygous phenotype
59
Intraspecific variation
Between members of a population and between membres of a species
60
Interspecific variation
Between members of different species
61
Causes of phenotypic variation | 2
Genetic variation between individuals due to different individuals possessing different allele combinations Environmental differences between individuals
62
Causes of genetic variation | 2
Gene mutations to create new alleles Crossing over of non sister chromatids of homologous pairs in meiosis 1 Independent segregation of homologous chromosomes in meiosis 1 Random fusion of gametes
63
Evolution is
The change in allele frequency in a population over he course of many generations
64
Two causes of evolution
Natural selection Genetic drift- in small populations
65
Natural selection
Changes allele frequency in populations over the course of many generations
66
Natural selection | 7
- individuals subject to selection pressure such as competition, predation, disease - phenotypic variation due to genetic variation, different combinations of alleles - there is differential reproductive success - individuals with advantageous alleles have reproductive success - process repeated over many generations - frequency of advantageous alleles in gene pool increases - population becomes more adapted to its environment
67
Stabilising selection | 4
Occurs in a stable environment Individuals with extremes of phenotypes have lower reproductive success Mean phenotype remains unchanged but more of the population becomes closer to the mean Standard deviation and range is reduced
68
Directional selection | 3
Occurs when the environment changes Individuals with phenotype of one extreme have higher reproductive success Mean phenotype in the population shifts towards the favoured extreme over many generations
69
Disruptive selection | 3
Occurs when the environment favours individual of both extreme Individuals with phenotype of both extreme have increased reproductive success After many generations it may result in two different breeding populations- speciation
70
Genetic drift
The random changes in frequency due to chance rather than natural section
71
Genetic drift process | 4
Individuals in a population show variation in their phenotype By chance those with one allele happen to have more offspring so more of the population carry the allele By chance the process is repeated, those with the allele produce more offspring and the frequency of the allele increases in the population If enough differences inn allele frequency build up over many generations genetic drift can lead to speciation
72
Genetic drift is. More evident in small populations because
Chance differences are less likely to cancel each other out. In a small population,small populations have a bigger effect Genetic drift increases the genetic diversity of a population
73
Speciation
The development of a new species from an existing species
74
A population becomes a new species when
It’s members can no longer interbreed with and produce fertile offspring with the original population
75
Two forms of speciation
Allopatric and sympatric
76
Allopatric speciation
Occurs when two populations become physically separated and there is no interbreeding / gene flow between the populations
77
Allopatric speciation process | 6
A sub group becomes geographically isolated by physical barrier Isolated population experiences different environmental conditions an directional selection will occur changing allele frequency Different random mutations will occur in isolated and original population Genetic drift will occur changing allele frequency in isolated population After many generations, individuals from the isolated populations allele frequency wil be so different that they willl no longer be able to interbreed to produce fertile offspring with the original population So many differences in gene pool that the two populations are reproductively isolated
78
Sympatric speciation
When two populations are still occupying the same habitat but a change has occurred to stop them interbreeding with one another Two populations become reproductively isolated and stop interbreeding
79
Mechanisms of reproductive isolation Sympatric speciation 3
Seasonal changes= due to a mutation some plants may flower at a different time of the year , they can therefore only interbreed with plants flowering at the same time Mechanical changes= gene mutations which lead to changes in size and functioning of the genitalia making mating between two sub groups physically impossible Behavioural changes= a sub group may develop. A different courtship ritual that only attracts mates within the sub group

Biology A Level (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions