Genetics Flashcards
(132 cards)
1
Q
What is a gene?
A
A gene is a stretch of DNA that codes for a trait. In molecular biology- it codes for a protein, which acts to bring about a trait.
2
Q
What is a phenotype?
A
What is observed, such as height, color
3
Q
What is a genotype?
A
The genetic make up- such as homozygous dominant(TT), heterozygous(Tt) or homozygous recessive( tt)
4
Q
What is a locus?
A
Location of a gene on a chromosome
5
Q
What is an allele?
A
A variant of a gene
6
Q
Explain the relationship between a gene and allele
A
An allele is a variant of a gene
- a gene may have a number of alleles
- all alleles of the same gene exist at the same locus
7
Q
How many alleles does a cell hold?
A
A cell holds 2 alleles, one from each parent
8
Q
What is a homozygous genotype?
A
When two alleles that an individual carries are the same.
9
Q
What is a heterogenous genotype?
A
When the two alleles that an individual carries are different
10
Q
What is the wild type of a genotype?
A
The normal allele or phenotype of an organism.
-Usually the most prevalent, although it doesn’t have to be
11
Q
What is recessiveness?
A
The weak allele. Expressed only if both copies are present.
12
Q
What is expressively?
A
The degree to which a penetrant gene is expressed
13
Q
What is penetrance?
A
The frequency that a genotype will express the phenotype.
14
Q
What is a leakage?
A
Gene flow from one species to another
15
Q
Give 3 contrasts between meiosis and mitosis
A
- no tetras in mitosis, tetras formation in meiosis leads to crossing over
- mitosis results in diploid(2n) daughter cells while meiosis results in haploid(n) daughter cells
- in mitosis, daughter cells are identical to parent cell while daughter cells are different to parent cell in meiosis
16
Q
Contrast mitosis and meiosis in terms of their final products
A
Mitosis- 2 daughter cells
Meiosis- 4 sperm cells or 1 egg(with polar bodies)
17
Q
Contrast mitosis and meiosis in terms of the number of divisions involved
A
1 division involved in mitosis.
2 divisions involved in meiosis
18
Q
Describe the mechanism of independent assortment
A
- In metaphase 1 of meiosis
- Random orientation occurs between homologous chromosomes along the metaphase line( any parents chromosome can be on any side)
- In anaphase 1 of meiosis, homologous chromosomes are pulled apart.
- those on the left will be put into one daughter cell, those on the right will be put into another
19
Q
What is the significance of meiosis?
A
Meiosis introduces genetic variability by genetic recombination.
Genetic recombination is the production of independent assortment and crossing-over, which introduces genetic variability
20
Q
Put it simply, what is the overall result of independent assortment?
A
A cell has 2 copies of chromosomes, each from a parent.
Independent assortment shuffles these chromosomes and places one copy of each gamete
21
Q
What does it mean for genes to be linked?
A
Genes are linked when they are on the same chromosome.
When genes are further apart on the same chromosome, they are less linked.
22
Q
What is a limitation to the randomization of independent assortment?
A
Genes on the same chromosome cannot be randomized by independent assortment
23
Q
What is the function of crossing over?
A
A mechanism that reduces linkage
Only efficient when genes are physically apart from each other on the same chromosome
24
Q
What is the function of recombination?
A
The process that introduces genetic diversity into the gametes during meiosis
25
What are the 2 processes that makeup recombination?
- Independent assortment
| - Crossing over
26
When does crossing over occur?
In prophase 1
27
What are single crossovers?
Chromatids exchange alleles at a given locus resulting in genetic recombination.
Results in 2/4 recombinants
28
What is the site of crossing over?
Chiasma
29
How is the chiasma created?
Chiasma made possible because of pairing of homologous chromosomes called a tertiary
Tetrahydrofuran is formed by synapsis
30
Distinguish double crossing over scenario 1 from scenario 2 and 3
- Scenario 1 does not result in genetic recombination
| - Scenario 2 and 3 result in genetic recombination
31
Describe scenario 1 of double cross over
The chromatids involved in double cross over exchange alleles but exchanges them back.
This is the 2-strand double cross over.
Results in 0/4 recombinants
32
What is scenario 2 of double cross overs?
The chromatids exchange alleles during cross over.
Then one of the crossover chromatids exchanges with a different chromatid.
This is the 3 strand cross over
Results in 2/4 crossing over
33
Describe scenario 3 of double cross over
The chromatids exchange
Then 2 totally different chromatids on the same chromosome exchange
This is called 4-strand double crossover.
Results in 4/4 recombinants
34
What is the synaptnemal complex?
The protein complex that glues the tetras complex
35
What is a tetrad?
The paired homologous chromosome structure
36
What are sex-linked characteristics?
The gene for a characteristic is on the X chromosome
37
Why are there very few genes on the Y chromosome?
- The Y chromosome is very small chromosome and carries few genes of importance
- All sex-linked alleles are carried on the X chromosome
38
What determines cytoplasmic inheritance?
Inheritance of other things aside from genomic DNA
39
What determines inheritance of cellular organelles?
Inherited from mother
40
What is a mutation?
Change in DNA sequence by any means other than recombination
41
List the types of mutations
1. Random mutation
2. Translation error
3. Transcription error
4. Base substitution
5. Inversion
6. Addition/insertion
7. Deletion
8. Translocation
9. Mispairing
42
What is random mutation?
Random changes in DNA sequence, can be due to radiation, chemicals, replication error...etc
43
What is a translation error?
Even if the DNA for a gene is perfect, errors during translation can cause expression of a mutant phenotype
44
What is a transcription error?
Even if the DNA is perfect, errors during transcription can cause expression of a mutant phenotype
45
What is base substitution mutation?
Mutation involving a base( ATCG) turning into another base
46
What is inversion mutation?
A stretch of DNA breaks off(segment of a chromosome), then reattaches in the opposite orientation
47
What is the addition/insertion mutation?
An extra base is added/inserted into the DNA sequence
48
What is deletion mutation?
A base is taken out of the DNA sequence
49
What causes addition/insertion and deletion mutation?
Result in a frameshift mutation
50
What is translocation mutation?
A stretch of DNA(segment of a chromosome) breaks off, then reattaches somewhere else
51
What is mispairing mutation?
A not pairing with T
Or
G not pairing with C
52
What is advantageous mutation?
Results in a benefit to the fitness of the organism
53
Give an example of an advantageous mutation
Mutation that causes flies to become wingless is advantageous in an environment where it is very windy
54
What is a deleterious mutation?
Results in a harmful effect to the fitness of the organism
55
Give an example of a deleterious mutation
A mutation that causes an organism to be sterile
56
What are inborn errors of metabolism?
Genetic diseases resulting in faulty metabolism
57
What is Phenylketunoria(PKU)?
An inborn error of metabolism where people can’t metabolism phenylalanine.
58
Discuss treatments and cure for Phenylketonuria(PKU)
No cure but treatments involve avoiding the amino acid phenylalanine
59
What is a mutagen?
Something that leads to a mutation
60
What is a carcinogen?
Something that causes a mutation that causes cancer
61
All carcinogens are __________ . But not all mutagens are ______________
Mutagens
Carcinogens
62
What is genetic drift?
Random changes in allele frequency due to chance and not due to natural selection
63
What are the 5 assumptions of the Hardy-Weinberg principle?
- Infinitely large population(no genetic drift)
- No mutation
- No migration
- Random mating(no sexual selection)
- No natural selection
64
Give the mathematical formulas of the Hardy-Weinberg principle
p+q=1
(p+q)^2= 1= p^2+2pq+q^2=1
65
What is a back cross?
Mating between the offspring and parent- preserves parental genotype
66
What is the parental generation?
P-generation of a parent. On a pedigree that represents this row represents the parents
67
What is the Felial 1/ children on a pedigree chart?
F1 generation- on a pedigree, this is the row below the parents/ represents the children of the parents
68
What is felial 2/ grandchildren on a pedigree chart?
F2- on a pedigreee this is below to F1 and represents the grandchildren of the parents
69
What is gene mapping?
Physical location of genes on a chromosomes( toward the end for example)
Further apart = higher crossover frequency
70
What is biometry?
Using statistics to analyze biological data
71
What is the null hypothesis in biometry?
First assuming that you are wrong- there is no relationship in your data
72
What is the use of t-tests in biometry?
Compares 2 data tests
73
What is the use of ANOVA in biometry?
Compares 3+ data tests
74
What is the p-value in stats?
Calculated chance that the null hypothesis is right, the chance you are wrong
75
What is the significance of a p-value being less than 0.05?
0.05 means less than 5% chance the null hypothesis is correct(reject the null hypothesis)
76
What is the Fischer exact test?
Compares data in a 2x2 table
77
Discuss skewness
Skew- asymmetry in the bell curve
Skewed left- longer “tail” of the bell curve on the left
78
What can be used to analyze the distribution of a single data set?
Standard deviation/ variation
79
How is DNA converted to an mRNA transcript?
1. Add hydroxyl group to the 2’ carbon of each deoxyribose. In biochemist speak, you hydroxylate the 2’ deoxyribose
2. Snip the methyl group off of every thymine that occurs in the nucleotide strand. In biochemistry speak, you demethylate each thymine to uracil
80
Give the differences in and similarities in nucleotide bases in DNA and RNA
DNA- Adenine, thymine, cytosine and guanine
RNA- Adenine, uracil, guanine, cytosine
81
Differentiate the sugar in nucleotide in DNA and RNA
DNA- deoxyribose
RNA- ribose
82
What is the function of DNA?
Information storage
83
What are the type of bonds between nucleotides in DNA and RNA?
Phosphodiester bonds
84
What is complete dominance?
When only one dominant gene and one recessive allele exist for a given gene
85
What is codominance?
When more than one dominant allele exists for a gene such as AB blood type
86
What is incomplete dominance?
Occurrence when a heterozygote expresses a phenotype intermediate between two homozygous genotypes
87
Explain how penetrance effects the severity of Huntington’s disease
Huntington’s disease is caused by the repetitive sequence in the huntingtin gene
- Individuals with over 40 sequence repeats have full penetrance( 100% will show symptoms)
- fewer sequences show high penetrance, most people will show symptoms
- even fewer repeats the gene becomes low penetrance or nonpenetrant
88
Differentiate between constant expressivity and variable expressivity
Constant expressivity- all individuals with a given genotype express the same phenotype
Variable expressivity- individuals with the same genotype may have differing phenotype
89
Differentiate penetrance and expressivity
Penetrance- a population parameter that examines what % of individuals with a given genotype express a phenotype
Expressivity- explores expression on an individual level
90
Describe Mendel’s first law: law of segregation
1. Genes exist in alternative forms ( alleles)
2. An organism has 2 alleles form of each gene, one inherited from each parent
3. The 2 alleles segregate, each into a gamete during meiosis
4. If 2 alleles of an organism are different, only one will be fully expressed and the other will be silent(dominant and recessive)
91
Briefly state what is Mendel’s second law (of independent assortment)
States the inheritance of one gene does not affect the inheritance of another gene
92
Explain Mendel’s second law (of independent assortment)
Before meiosis 1, spermatogonia and oogonia undergo genome replication
In prophase 1 homologous chromosomes pair up to form tetrads and genetic material is swapped
93
What is natural selection?
The theory that certain characteristics or traits possessed by individuals to have greater reproductive success
94
Who and when did the natural selection theory develop?
Charles Darwin in his 1859 publication “On the Origin of Species”
95
What were the basic tenets that went into making the natural selection theory?
- Few offspring survive to reproductive maturity
- variations among individuals may be heritable and variations may be favorable
- individuals with these favorable variations have better fitness than those that dont
96
How does the modern synthesis model/neo-darwanism aid Darwinism?
Adds knowledge of genetic inheritance and changes to the gene pool to Darwin’s theory
97
What is differential reproduction?
When mutation or recombination results in a favorable change, it is more likely to pass to the next generation
The opposite is true
98
What is inclusive fitness?
A measure of an organisms success in the population
Based on number of offspring, success in supporting offspring and ability of offspring to support others
99
What idea/theory does inclusive fitness promote?
Promotes the idea that altruistic behavior can improve the fitness and success of a species
100
Describe the origins of punctuated equilibrium
Examination of the fossil records showed little evolution occurred within a lineage of life forms followed by quick bursts of evolutionary change
Niles Elridge and Stephen Jay Gould proposed punctuated equilibrium in 1972 to contented with Darwin’s theory
101
What are the modes of natural selection?
Stabilizing selection
Directional selection
Disruptive selection
102
What is stabilizing selection ?
Selection that keeps phenotype in a specific range by selecting against extremes(human birth weight)
103
Why is it advantageous to keep the fetus birth weight to a narrow range?
Too little birth weight may not be healthy enough to survive
Too much can cause trauma when traveling through the birth canal and reqyiring more resources from the mother
104
What is directional pressure?
Adaptive pressure can lead to the emergence and dominance of an initially extreme phenotype
105
How can antibiotics cause directional selection in bacteria?
Giving antibiotics to bacteria will cause a new standard phenotype to emerge as a result of differential survivorship
106
What is disruptive selection?
When 2 extreme phenotypes are selected over the norm
107
Give an example of disruptive selection
Finches in the Galápagos Islands.
Beaks were either small or big with few medium sized due to the size of the seeds
108
What are polymorphisms?
Naturally occurring differences between members of the same population
This facilitates disruptive selection
109
What is adaptive radiation?
Concept of a rapid rise of a number of different species from a common ancestor
110
What is the benefit of adaptive radiation?
Allows various species to occupy different niches decreasing competition for resources
111
What is a niche?
A specific way of life including habitat location, utilization of resources
112
What is a species?
The largest group of organism capable if breeding to form fertile offspring
113
What is speciation?
The formation of a new species
114
Reproductive isolation may occur either ____________ or ___________
Prezygotically
Postsygotically
115
What are prezygotic mechanisms?
Prevent formation of the zygote completely
116
What are postzygotic mechanisms?
Allow for gamete fusion but yield either non viable or sterile offspring
117
What are examples of prezygotic mechanisms?
1. Temporal isolation
2. Ecological isolation
3. Behavioral isolation
4. Reproductive isolation
5. Gametic isolation
118
What is temporal isolation?
Breeding at different times
119
What is ecological isolation?
Living in different niches within territories
120
What is behavioral isolation?
A lack of attraction between members of the two species due to differences in pheromones,courtship...
121
What is reproductive isolation?
Incompatibility of reproductive anatomy
122
What is gametic isolation?
Intercourse can occur but not fertillization
123
Give examples of postzygotic mechanisms
Hybrid inviability
Hybrid breakdown
Hybrid sterility
124
What is hybrid inviability?
Formation of zygote that cannot develop to term
125
What is hybrid breakdown?
Forming first generation hybrid offspring that are visible and fertile but second generation are infertile and inviable
126
Mules are an example of__________
Hybrid sterility
127
What are the 3 patterns of evolution?
1. divergent evolution
2. Convergent evolution
3. Parallel evolution
128
What is parallel evolution?
Refers to the process whereby related species evolve in a similar way for a long time because of response of analogous environmental species
129
What is divergent evolution?
The independent development of dissimilar characteristics in 2 or more lineages sharing a common ancestor
130
What is convergent evolution?
Refers to the independent development of similar characteristics in two or more lineages sharing a common ancestor
131
How is the rate of evolution measured?
The rate of change of a genotype over a period of time
132
What is the molecular clock model?
The correlation of degree of genomic similarity with the amount of time since two species split off from the same common ancestor
The more similar the genomes, the more recently the two species separated from each other
