chapter 20 - patterns of inheritance Flashcards
1
Q
What is a diploid?
A
- an organism with a pair of homologous chromosomes, it has 2 alleles of each gene
2
Q
What is a gene?
A
- a sequence of dna that codes for a protein
3
Q
What is a allele?
A
- A variation of a gene
4
Q
What is a genotype?
A
- the combination of alleles that an organism has
5
Q
What is a phenotype?
A
- the physical expression of the genotype and its interaction with the enviornment (skin colour)
6
Q
What is a dominant allele?
A
- Its an allele that is always expressed in the phenotype
7
Q
What is a recessive allele?
A
- alleles that are only expressed when homozygous
8
Q
What are codominant alleles?
A
- both alleles are expressed in the phenotype, phenotype is intermediate for both alleles
9
Q
What is meant by homozygous?
A
- When both alleles are the same
10
Q
What is meant by heterozygous?
A
- when both alleles are not the same
11
Q
What is the locus?
A
- the location of a gene on a chromosome
- alleles of the same genes always have the same locus
12
Q
What is monohybrid inheritance?
A
- inheritance of a characteristic controlled by a single gene
13
Q
What is dihybrid inheritance?
A
- inheritance of two characteristics controlled by two separate genes
14
Q
What are the phenotypic ratios for both monohybrid and dihybrid inheritance?
A
- monohybrid - 3:1
- dihybrid - 9:3:3:1
15
Q
How do the gametes differ in codominance compared to both monohybrid and dihybrid inheritance?
A
- the gametes are heterozygous whereas in monohybrid and dihybrid the gametes are homozygous
16
Q
What is an autosome?
A
- all the non sex chromosomes
17
Q
what is autosomal linkage?
A
- its where genes that are on the same autosome are linked
- they will stay together during independant assortment and will be inherited together
- affects the typical phenotypic ratio(9:3:3:1)
- because linked genes are inherited together they behave more like monohybrid cross (3:1)
- autosomal linkage means that more offspring will have the same genotype and phenotype as their parents
18
Q
What may cause the offspring to not have the same genotype and phenotype?
A
- the alleles are separated during crossing over
19
Q
What makes genes more closely related?
A
- the closer their loci of genes on an autosome, the more closely linked they are
20
Q
What is a homologous pair?
A
- same genes
- different alleles
21
Q
What is sex linkage?
A
- the expression of alleles located on sex chromosomes depends on the sex of the individual
22
Q
What type of chromosomes do females and males have and what is the difference between them?
A
- females have XX chromosomes
- males have XY chromosomes
- the Y chromosome is smaller than X and is missing more genes present on X
23
Q
What is required in the chromosomes of males and females for them to have haemophilia?
A
- females, must be homozygous recessive to be a sufferer
- males, the one X chromosome they have must be the faulty allele to be a sufferer
24
Q
What is epistasis and when does it happen?
A
- its an interaction between genes . . . when the expression of one gene surpresses the expression of another gene
- it happens when a phenotype is controlled by more than one gene
25
What affect does epistasis have on dihybrid crosses?
- it changes the typical phenotypic ratio (9:3:3:1)
- if recessive epistatic alleles(9:3:4)
- if dominant epistatic alleles(12:3:1)
26
What changes the normal phenotypic ratios
- autosomal linkage
- sex linkage
- epistasis
27
What is genetic bottleneck effect?
Is it in the same geographical location or not?
- we start with a ancestral population
- theres a big decrease in the population this could be due to hunting
- happens in the same geographical location
28
What does the genetic bottleneck effect result in?
- few individuals survive
- decrease in genetic diversity, meaning fewer alleles in surviving population
- inbreeding
- genetic drift has a greater effect on smaller populations
29
What is founder effect?
Is it in the same geographical location or not?
- where a few organisms in a population become separated and create a new colony
- this can happen because the organisms get lost or environmental factors prevent them from staying within their population
- it happens in different geographical locations
30
What does the founder effect result in ?
- new colony formed by a small number of individuals
- genetic diversity decreased
- inbreeding
- genetic drift has a greater effect on smaller populations
- founders have few alleles
31
What is genetic drift?
- changes in allele frequency between generations due to random chance (e.g random fertilisation)
32
What is meant by random fertilisation?
- the allele passed to the zygote is random
33
What is a species?
- organisms that can reproduce to produce fertile offspring
33
What is a gene pool?
- all the alleles present in a population
34
What is the difference between a population and a community?
- population, all the organisms of a single species in one place at a time
- community, all the organisms of all the species in one place at one time
35
What is allele frequency?
- how common an allele is in the population
36
what is evolution with regards to this topic?
- a change in allele frequency overtime
37
What is meant by differential reproductive success?
- organisms with a phenotype better adapted to their enviornment have selective advantage and are more likely to survive and reproduce
38
what is speciation?
- the process of forming a new species
39
What is the hardy weinberg principle?
- a model that predicts the frequency of alleles, genotypes and phenotypes in a population
40
What does the hard weinberg principle predict?
- the frequency of alleles of a gene will stay constant over generations
41
What are assumptions does the hardy weinberg principle assume?
- no mutations
- no selection
- random mating
- large population(no genetic drift )
- no migration
42
When does speciation occur?
- it happens when populations become reproductively isolated(no gene flow between them)
43
What are the two types of speciation and what is the difference?
- allopatric speciation, geographical isolation leading to reproductive isolation
- sympatric isolation, non geographical isolation leading to reproductive isolation
44
What are some examples of sympatric speciation and allopatric speciation?
- allopatric speciation, a river could separate two populations and so that isolates reproduction
- sympatric speciation, examples include:
- seasonal, reproductively active at different times of the year
- behavioural, different courtship behaviour
- hybrid sterility, hybrids of two parents are infertile
- morphological, different shaped genatlia
45
What does speciation result in?
- variation exists in the population(s) due to mutations
- causes a change in allele frequency
- occurs over many generations(dodo)
- directional reproductive success
- different selection pressures and so directional selection of different phenotypes
46
What is artificial selection?
- when humans interbreed organisms with useful traits(phenotype) to improve their usefulness
47
What are some examples of artificial selection?
- dairy cows
- corn
- pedigree dogs
48
Explain how artificial selection is used in cows?
- a female with a desired trait is selected(high milk yield, high quality, disease resistant)
- select a male with a mother with desired trait
- cross breed them
- select the offspring with the highest trait
-repeat the process over many generations
49
Explain how artificial selection is used in corn?
- select plants with desirable trait (large ears of grain)
- cross breed them
- select offspring with the best desirable trait
- repeat over many generations
50
What are the advantages of artificial selection?
- increase in frequency of desirable traits
- bigger/amplified traits
- more efficient farming
51
What are the disadvantages of artificial selection?
- reduced genetic diversity
- increased expression of genetic disorders, as inbreeding results in the expression of recessive alleles
- ethical issues, pugs can breathe properly
52
