Patterns of Inheritance 6.2 Flashcards
1
Q
What is genotype and phenotype?
A
genotype = genetic makeup of an organism phenotype = visible characteristics of an organism
2
Q
What is phenotype affected by
A
Phenotype is influenced by environment and genotype
3
Q
What are three types of mutatgenic agents? Giev exmaples
A
Mutagenic agents:
- physical agents (xrays, gamma rays, UV)
- chemical agents ( mustard gas, reactive oxygen species)
- biological agents (viruses, food contaminations)
4
Q
What are two cjaactersitcis of mutstions during gamete fprmation?
A
Mutations during gamete formation:
- persistent (transmitted through generations and are unchanging)
- random (unneeded)
5
Q
What are two type of mutation? When do they occur?
A
Type of mutation:
- gene (occur during S phase)
- chromosome ( occur during meiosis)
6
Q
What are types of chromosome murtations?
A
Vhromosome mutations:
- deletion
- inversion
- translocation
- duplication
- non dysjunction—-aneuploidy
- polyploidy
7
Q
What is deletion?
A
Deletion is where part of the chromosome containing genes and regulatory sequences is lost
8
Q
What is inversion?
A
Inversion is where a section of the chromosome breaks off, turns 180 degrees and joins on again. The genes are all there but too far away bfrom their reguklatory nucleotide sequences to be properly expressed
9
Q
What is translocation?
A
Translocation is where part of one chromosk me breaks off and attaches to another chromosome
10
Q
What is duplication?
A
Duplication is where a piec eof chromosome is duplicated causing overexpression whivh can be harmiful. Too many of certain proteins or gene regulating nucleic acids may dirupt metabolism
11
Q
What is non disjunction?
A
Non disjunction is where one pair of chromosomes/ chromatids fail to separate, leaving one gamete with an extra chromosome. When fertilised with a haploid gamete the resulting zygote has an extra chromosome
12
Q
What is aneuploidy?
A
Aneuploidy is a type of non disjunction. The chromosome number is not an exact multiple of the haploid number for that organism. Sometimes chromosomes or chromatids fail to separate so gametes have an extra chromosome at a certain postion
13
Q
What is polyploidy?
A
Polyploidy occurs in plant cells where they have more than two sets of chromosomes (e.g all cells have 3 sets)
14
Q
How can enireonament and genes interact? Example
A
Interaction of environment and genes:
- having the genes for a certain characteristic but he environment preventing their expression
- chlorotic plants. plants kept in dim light after germination/ soil has insufficient magnesium, they don’t develop enough chlorophylls so appear yellow/ white. So without the chlorophylls they cannot photosynthesise even thought they should be able to
15
Q
How can meiosis produce genetic variation?
A
Genetic variation from meiosis:
- crossing over in prophase 1
- independent assortment of chromosomes in metaphase/ anaphase 1
- independent assortment of chromosomes in metaphase/anaphase 2
16
Q
What is herterozygous?
A
Heterozygous is where something is not true breeding. They gave different alleles at a particular gene locus on a pair of homologous chromosomes.
17
Q
What is homozygous?
A
Homozygous is where something is true breeding. They have identical alleles at a particular gene locus on a pair of homologous chromosomes
18
Q
What is monogenic?
A
Monogenic is where something is determined by a single gene
19
Q
What is a monohybrid cross?
A
A monohybrid cross shows the genotyoes and ohenotypes of parents and offspring of a characteristic caused by one gene. (e,g, tall or short)
20
Q
What did mendel do as a monohybrid cross?
A
Mendels monohybrid crossmated 2 true breeding parent strains and then allowed the next gernartiom to self fertilise resulting in a 3 tall : 1 short ratio
21
Q
What is a punnet square?
A
Punnet squares have all possibke gametes are assigned a row; female to the vertical column and male to the horizontal column
22
Q
What is the Test Cross?
A
Test Cross is used to work out genotypes of phenotypically similar inviduals. The organism with dominant phenotype but unknown genotype is crossed with a recessive phenotype. If any offspring have the recessive phenotype we know the unknown organism is heterozygous.
23
Q
What is codominace?
A
CoDominace is where bith alleles present in the genoype of a heterozygous individual contriube to its phenotype
24
Q
What is an example of codomicnace?
A
Codimance in short horn cattle: coat colour has two alleles; Cr and Cw
- homozygous red coat CrCr have a red coat
- homozygous for whute coat CwCw have a white coat
- heterozygous CrCw have a roan coat
25
What happens if
- 2 roan cattle interbreed
- 1 red and 1 white cattle are interbred?
2 roan cattle produce a ratio-- 1 white: 2 roan : 1 red
| 1 red + 1 white produce all roan
26
What are some examples of codominance in humans?
Codimance in humans:
- AB blood groups
- sickle cell anaemia
- MN blood groups (code for a protein on the surface of ethyrocytes
27
What is an example of codominance in plants?
Codminance in plants:
| -Camelias have red and white flowers. But when corses both get expressed resulting in spotted flowers
28
What is multiple alleles?
Multiple alleles are characteristics for which there are 3 or more alleles in the population gene pool
29
What is an example of multiple alleles?
Multiple alleles are shown in blood groups. They demonstrate dominance and codominance
- Ib Io = group b (dominant)
- Ia Io = group A (dominant)
- Io Io = group o (recessive)
- Ia Ib = group AB (codominant)
30
What does it mean when genes are sex linked?
Sex linked is when a gene is only present on one of the sex chromosomes
31
What are autosomes?
Autosomes are the 22 chromosomes that aren't sex chromosomes. Each pair is homologous
32
What are the chromsomes of male and females? What is different abut the male's?
```
XX = females
XY = males, these are not fully homologous as only a small part of one of them matches a small part of the other just so they can match up before meiosis
```
33
Dsicuss the difference in inheriting an X chromosome with an abnormal allele for males and females.
Female with abnormal allele on X = she probably has a functioning allele on the other X so abnormality is not expressed
Male with abnormal allele on X = He does not have a functioning allele for that gene so even if the abnormality is recessive, he will have the disorder
34
How do we refer to males with x linked genes?
Males are functionally haploid for X linked genes as they will get a recessive disorder if they have one recessive allele present on the X because they have no functional allele to match it on the Y
35
What is an example of a sex linked disorder?
Sex linked disorder = Haemophilia A
Only present in males. For females Xh Xh is fatal.
The person is unable to clot bood fast enough.
If a female passes the X with the faulty allele to her son, he wil have no functioning allele to match it so he will get haemophilia A
36
What is the faulty allele for haemophilia?
Xh is the non functioning factor 8
37
What is a sex linked disorder other than haemophilia A?
Another sex linked disorder is colour blindness. There is a mutated colour vision gene on the X chromosome
38
Briefly describe sex linkage in cats
Coat colour shows sex linkage in cats.
Males cant be tortoise shell as they only have one X chromosome and they need both Cb and Co for tortoiseshell so they cant only ever have either Cb or Co
39
Why do females not have twice the number of X linked genes expressed than male?
It may appear that females have twice the number of X linked chromosomes than males. But in every female nucleus one of the X chromosomes is randomly inactivated in early embryonic development. This is called INACTIVATION OF X CHROMOSOMES IN FEMALE MAMMALS
40
what is dihybrid and dihybrid crosses?
Dihybrid means involving two gene loci.(on different chromosomes) So dihybrid crosses investigate the simultaneous inheritance of 2 characteristics (e.g. wrinkled and yellow)
41
How many combinations to hetero zygotes produce?
Heterozygotes always produce 16 combinations
42
What ration of offspring do heterozygotes produce?
Heterozygotes produce a ratio of 9:3:3:1
43
What did Mendel conclude from his dihybrid crosses?
Mendel deduced from his dihybrid crosses that :
- the alleles of two genes are inherited independently of each other, so each gamete has one allele for each locus
- During fertilization any one of an allele pair can combine with any one of another allele pair
44
What should a genetic diagram contain?
* Parent phenotypes
* Parent genotypes
* Parent gamete genotypes
* Punnett square
45
What is autosomal linkage?
Autosomal linkage = linked genes which are inherited together that are on a non-sex chromosome
46
What is an autosome?
Autosomes are non-sex chromsomes
47
How do automsomal genetic diagrams look different?
Autosomal genetic diagram have the gametes genotypes as one above and one below each other instead of next to (e.g. not Gn but G/n)
48
What are recombinant gametes?
Recombinant gametes are gametes containing new combinations of alleles due to crossing over at prophase 1 in meiosis. These are more likely to occur when 2 gene loci on the chromosome are further apart
49
When are recombinant gametes more likely to occur?
Recombinant gametes are more likely to happen if the 2 gene loci are further apart because if they cross over its more likely they will not stay together
50
What happens if autosomally linked genes are not affected by crossing over? If they are?
If autosomally linked genes are not affected by crossing over then they are always inherited as a unit. If they are affected by crossing ove they may not be inherited as a unit resulting in recombinant gametes
51
Why may you get unexpected phenotypes? (autosomal linkage)
You may get unexpected phenotypes due to crossing over and recombinant gametes
52
What is epistasis?
Epistasis is the interaction of non linked genes where one masks the expression of the other (affects phenotypic characteristic). Thye may work antagonistcally or complimenarily
53
What are the three types of epistasis?
Types of epistasis;
- recessive epistasis
- dominant epistasis
- Complimentary gene action
54
What is recessive epistasis?
Recessive epistasis where the homozygous presence of a recessive allele at the first locus prevents the expression of the allele at the second locus (9:3:4 )
- alleles at the first locus are epistatic to the second locus
- alleles at the second locus are hypostatic to those at the first locus
55
What does hypostatic mean?
| What does epistatic mean?
Hypostatic is the gene that gets masked by the epistatic gene
Epistatic is the gene that masks the hypostatic gene
56
What is dominant epistasis?
Dominant epistasis is where having at least one dominant allele at the first loci will mask the effect of the second locus ( 12:3:1 or 13:3)
57
What is complimentary gene action?
Complimentary gene action is where both gene locus have effect to create different colour combinations
Genes work to code for 2 enzymes that work in succession, catalysing sequential steps of a metabolic pathway ( 9:7 or 9:3:4 or 9:3:3:1 )
58
Give a brief example of complimentary gene action
Complimentary gene action:
- C (first gene locus) determines whether the coat has colour by coding for an enzymes to turn the colourless precursor molecule into black pigment
- A (second gene locus) codes for agouti colour by coding for an enzyme turning black pigment into agouti
- aa produces black colour
59
What does a 12:3;1 ratio suggest?
12:3:1 suggests dominant epistasis
60
What does a 13:3 ration suggest?
13:3 ratio suggests dominant epistasis
61
What does a 9:3:4 ratio suggest?
9:3:4 ratio suggest recessive epistasis
62
What does a 9:7 ratio suggest?
9:7 suggest complimentary gene action
63
What does a 9: 3:4 ratio represent?
9:3:4 ratio suggest complimentary gene action
64
What does a 9:3:3:1 ratio represent?
9:3:3:1 ratio represents complimentary gene action
65
What is speciation?
Speciation is the splitting of genetically similar population into 2 or more populations that undergo genetic differentiation and eventually reproductive isolation leading to evolution of 2 or more new species
66
What is allopatric speciation?
Allopatric speication is formation of two different species from an original species due to geographical isolation
67
What is sympatric speciation?
Sympatric speciation is the formation of 2 different species from the original species due to reproductive isolation while the populations inhabit the same geographical location
68
What is a sub species?
Subspecies are where two populations are different but are still able to interbreed during the evolutionary process
69
What does geographical isolation lead to?
geographical isolation leads to allopatric speciation
70
What does reproductive isolation lead to?
Reproductive isolation leads to sympatric speciation
71
What are two isolating mechanisms?
Isolating mechanisms:
- geographical isolation
- reproductive isolation
72
Discuss geographical isolation
Geographic isolation:
- populations separated by geographical features acting as barriers to gene flow
- selectional pressures are different so independent changes to allele frequencies/chromosome arrangement
- genetic changes may be due to a mutation, natural section or genetic drift
- each population becomes adapted to its new environment
73
What is reproductive isolation?
Reproductive isolation is biological and behavioral changes within a species that may lead to reproductive isolation from one another (prevents mating)
74
What are genetic changes that may cause reproductive isolation?
Genetic causes for reproductive isolation:
Changes in chromosome numbers may
-prevent gamete fusion
-make zygoytes less viable so they fail to develop
-lead to infertile offspring hybrids with an odd number of chromosomes so that chromosome pairing in meiosis cant occur
75
What are non genetic changes that may cause reproductive isolation?
Non genetic causes of reproductive isolation:
- change in courtship behavior
- change in genitalia or plant/flower structure
- change in foraging behavior meaning they are active at different times of the day
76
What are the 3 phrases that describe when an animal is active?
Diurnal - active during the day
Crepuscular - active at dawn and dusk (twilight)
Nocturnal - active at night
77
What is artificial selection?
Artificial selection = selective breeding of organisms
humans chose desired phenotypes and interbreed the phenotype individually, therefore selecting what genotypes contribute to the gene pool of the next generation and preventing others breeding
78
What are 2 desired plant characteristics?
Desirable plant characteristics:
- increased yield
- pest and disease resistance
79
What are 4 desired animal characteristics?
Desirable animal characteristics:
- docility
- placidity
- ability to be trained
- high yield of meat and milk
80
What is a negative side effect of selective breeding?
Negative:
- inbreeding depression
genetic diversity in the gene pool is reduced. If related organisms are crossed it can result in inbreeding depression. The chances of an individual inheriting 2 copies of a recessive allele are increased
81
What is hybrid vigour?
Hybrid vigour is where individuals are out breed/out crossed to obtain individuals that are heterozygous at many gene loci. This produces individuals more like their wild ancestors. (e.g cross breed dogs)
82
How can new breeds be produced?
New breeds can be produced by selective breeding programmes
83
What are some examples of gene banks?
Gene banks:
- rare breed farms
- wild populations of organisms
- crops in cultivation
- botanic gardens and zoos
- seed banks
- sperm banks
- cells in tissue culture
- frozen embryos
84
What are ethical consideration of selective breeding?
Ethical considerations:
- domesticated animals retain juvenile characteristics so are less able to defend themselves + loss of nervous disposition makes them easy prey
- live stock animals have more lean meat than fat so succumb to cold temps if not housed
- dog coats are bad camoflage
- dogs inbreeding results in susceptibility to disease
- traits desired by humans may lower survival in wild
85
What is the chi squared test?
Chi squared test= statistical test designed to find out if the difference between observed and expected data is significant or due to chance. In genetics you do not want a difference to what expected
86
What is the null hypothesis?
Null hypothesis = there is no statistically significant difference between the observed and expected data. Any difference is due to chance
87
How do you calculate the degrees of freedom/
degrees of freedom = number of categories-1
88
How would you set up a table to calculate chi squared?
```
6 columns:
-category
-observed data O
-expected data E
- O - E
-( O - E )2
-( O - E )2 / E
Then total of the 6th column
```
89
How do you work out the expected results for the chi squared test?
Expected results
find the ratio there should be (e.g. 9 :3:3:1 )
calculate the fraction of the overall number of readings each bit of the ration should be
(e.g 9/16 of 288)
90
What is continuous variation?
Continuous variation is variation that produces phenotypics variation where the quantitave traits vary vby verys amll amounts between one group and the next
91
What is discontinuous variation?
Discontinuous variation is genetic variation producing discrete phenotypes- two or more non overlapping categories
92
Discuss discontinuous variation in terms of alleles
Discontinuous variation has no intermediates between different phenotypes. These characteristics are usually determined by the alleles of a single gene locus. They are monogenic.
Some alleles interact to govern a single characteristic
93
Discuss continuous variation in terms of alleles
Continuous variation is where many genes are involving in determining the characteristic, the characteristics are polygenic. Each allele may contribute a small amount to the phenotype so the alleles have an additive effect on the phenotype
94
How does the environment affect monogenic and polygenic characteristics
The environment affects polygenic characteristic more.
| e.g. height and malnutrition
95
What the diffreence between polygenic and mongenic characteristics?
Monogenic characteristic = determined by the alleles of a single gene locus
Polygenic characteristic =
96
What is natural selection? (include allele frequency)
Natural selection where some individuals are better adapted to their environment and so are more likely to survive and reproduce, passing the advantageous characteristics o to the offspring. Over time allele frequency will change
97
How are new alleles introduced?
New alleles are introduced by mutations and migrations
98
What are three types of selection?
Types of selection:
- stabilising
- directional
- disruptive
99
What is stabilising selection?
Stabilizing selection favours the intermediate phenotypes (average). This occurs when the environment remains unchanged
100
What is directional selection?
Directional selection is where the environment changes resulting in a feature being more advantageous than before. shift So overtime, left to reproduce and survive, the optimum value gradually shifts (the averages)
101
What is disruptive selection?
Disruptive selection favours both extreme phenotypes and the intermediates are selected against as a result of drastic environmental change. This can result in speciation
102
Compare graph shapes for the types of selection
Stablising selection = bell shaped
Directional selection = two overlapping peaks, the same peaks but one shifted
Disruptive selection = two peaks with an upside down bell shape in the centre
103
What is genetic drift?
Genetic drift occurs by chance events on a small population. Small populations lack genetic variation so catastrophic events an allele may entirely disappear. When the population recovers and increases in size it will have less genetic diversity than before
104
What can genetic drift arise from?
Genetic drift arises from a genetic bottle neck or the founder effect
105
What is the founder effect?
The founder effect = new population of a small number of individuals who originate from a larger, parent population. The new population is likely to experience loss of genetic variation
106
Discuss a genetic bottle neck
Genetic bottle neck:
- population size shrinks and grows again
- genetic diversity reduced and loss of advantageous alleles/ disproportional amount of harmful alleles
- drastic shrink means fertility is affected leading to endangerment and extinction
107
What happens if the surviving have a advantage after a genetic bottle neck?
If after a genetic bottle neck the ones that survive are at an advantage then the bottleneck improves the gene pool but shrinks genetic diversity
108
What does the hardy Weinberg principle explain?
The Hardy Weinberg principle describe and predicts a balanced equilibrium in the frequencies of alleles and genotypes within a breeding population
109
What can the hardy Weinberg principle be used for?
Hardy Weinberg Principle can be used to determine the frequency of those carrying s recessive allele for a genetic disorder
110
What are the 4 assumption of the hardy Weinberg principle?
Assumptions of the hardy Weinberg principle:
- population is large enough to make sampling errors negligible
- mating within a population occurs at random
- no mutation, migration or genetic drift
- there is no selective advantage for any genotype and therefore no selection
111
What does P and q stand for in the hardy Weinberg equations?
```
P = dominant allele
q = recessive allele
```
112
What do the following combinations represent?
- p2
- q2
- pq
```
P2 = homozygous dominant
q2 = homozygous recessive, ill
pq = heterozygous, symptom less carrier
```
