✅Transmission Genetics - Leslie Turner Flashcards
1
Q
How do eubacteria replicate?
A
With a single origin of replication, high rate of reproduction, genes near ORI site and more highly expressed operon structure
2
Q
What happens in G1 phase of mitosis?
A
The cell grows, mRNA and proteins synthesised
3
Q
What happens in G0 phase of mitosis?
A
Cells may enter a non-dividing phase
4
Q
What happens after the G1/S checkpoint of mitosis?
A
The cell is committed to dividing
5
Q
What happens in S phase of mitosis?
A
DNA duplicates
6
Q
What happens in G2 phase of mitosis?
A
The cell prepares for mitosis
7
Q
What happens after the G2/M checkpoint of mitosis?
A
The cell can divide
8
Q
What happens in prophase?
A
Chromosomes become visible after duplication, the mitotic spindle forms
9
Q
What happens in prometaphase?
A
Disintegration of the nuclear membrane marks the start of prometaphase, and the spindle microtubules attach to chromatids
10
Q
What happens in telophase?
A
Chromosomes arrive at spindle poles, the nuclear membrane re-forms and the chromosomes relax
11
Q
What happens in anaphase?
A
Sister chromatids separate and move towards opposite poles
12
Q
What happens in metaphase?
A
Chromosomes line up on the metaphase plate
13
Q
In which stage of mitosis does the number of chromosomes per cell double?
A
8
14
Q
What happens on meiosis I?
A
The separation of homologous chromosomes to produce two diploid daughter cells, crossing over takes place
15
Q
What happens in meiosis II?
A
The separation of sister chromatids to produce four haploid daughter cells
16
Q
What is the period between meiosis I and II called?
A
Interkinesis
17
Q
What is crossing over?
A
The swapping of genetic material between homologous chromosomes
18
Q
How does gametogensis and fertilisation lead to variation?
A
The sperm and the egg that fuse will contain different genes
19
Q
What are the two classifications of mutations?
A
Somatic or germ line
20
Q
What is a substitution?
A
One base is replaced by another
21
Q
What is a transversion?
A
Changing a purine to a pyrimidine or vice versa
22
Q
What is a transition?
A
Changing a purine for another purine or a pyrimidine for another pyrimidine
23
Q
What is a point mutation?
A
A change to a single nucleotide in a DNA sequence that doesn’t change its length
24
Q
What are expanding nucleotide repeats?
A
Mutations in which the number of copies of a set of nucleotides increases in number
25
What is a forward mutation?
One which changes the wild-type phenotype
26
What is a reverse mutation?
One which changes the phenotype back to the wild type
27
What is a missense mutation?
A substitution that results in a different amino acid in the protein
28
What is a nonsense mutation?
One which changes a sense codon (one that specifies an amino acid) into one that terminates translation
29
What is a silent mutation?
Changes a codon to a synonymous codon that specifies the same amino acid
30
What are incorporation errors and replication errors?
When a mismatched base has been incorporated into a newly synthesised nucleotide chain
31
What can cause a replication error?
Wobble
32
What causes wobble?
A base mismatch, eg thymine pairing with guanine
33
How does strand slippage occur?
When one nucleotide strand forms a small loop
34
What is unequal crossing over?
Caused by misaligned pairing, one DNA molecule has an insertion and the other has a deletion
35
What is depurination?
The loss of a purine through hydrolysis
36
What does depurination form?
An apurinic site
37
What is deamination?
The loss of a amino group, to form a different base eg C to U
38
What are base analogs?
Chemical structures similar to any of the bases
39
What is a pyrimidine dimer?
Two thymine bases block replication, can be induced with UV radiation
40
What are alkylating agents?
Chemicals that donate alkyl groups, EMS can add an ethyl group to guanine, producing a base like structure that pairs with guanine
41
What is hydroxylamine?
A specific base modifying mutagen that adds a hydroxyl group to cytosine
42
What is repeat expansion?
A special case of insertion, increase in the number of copies of nucleotides, during replication a hairpin occurs and loops back, pairing with itself and causing part of the template to be replicated twice
43
Why is there a male mutation bias?
Due to the continuous production of sperm compared to female eggs
44
What is a suppressor mutation?
Mutation that hides or suppresses the effect of another mutation
45
What is an intragenic suppressor mutation?
Occurs in the gene containing the gene being suppressed
46
What is an intergenic suppressor mutation?
Occurs in a gene other than the one bearing the original mutation
47
How can intragenic suppressors work?
It may change a second nucleotide in the same codon altered by the original mutation, producing a codon that specifies the same amino acid that is specified by the original, unmutated codon
48
How can intergenic suppressors work?
Sometimes work by changing the way that the mRNA is translated
49
What do chromosome mutations include?
Rearrangement, aneuploidy and polyploidy
50
What do rearrangements include?
Duplication, deletion, inversion, translocation
51
What is duplication?
A segment of the chromosome is duplicated
52
Where do most duplications occur?
Within the same chromosome (intra-chromosomal)
53
What is a tandem duplication?
If duplications occur next to one another
54
What is a reverse duplication?
Where the segment is flipped over
55
What has to happen to the duplicated chromosome in prophase?
It has to loop out to align with the homologus chromosome
56
How can duplication alter phenotypes?
It can alter gene dosage
57
Why does chromosome duplication affect gene dosage?
It produces extra copies of some but not all genes
58
What are segmental duplications?
Anything of more than 1000 base pairs, anything less is an indel
59
What is an inversion?
A segment of the chromosome is turned 180 degrees
60
What is a paracentric inversion?
When the centromere is unaffected
61
What is a pericentric inversion?
When the centromere is affected
62
How would abnormal gametes be formed by chromosome mutation?
In a heterozygote, a single crossover with a paracentric inversion would lead to abnormal gamete
63
How do pericentric inversions affect gametes?
They have chromosomes of normal size but have too many or too few of some genes
64
What is translocation?
Movement between non-homologous chromosomes
65
What forms can translocations be?
Reciprocal, non-reciprocal or Robertsonian
66
What is a reciprocal translocation?
When there is a two way exchange of segments between the chromosomes
67
What is a Robertsonian translocation?
When the short arm of an acrocentric chromosome is exchanged with the long arm of another
68
What is an acrocentric chromosome
Centromere at the end
69
What is a metacentric chromosome?
Centromere in the middle
70
What is aneuploidy?
The presence of an absnormal number of chromosomes in a cell
71
What is nullisomy?
Loss of a homologous pair
72
What is monosomy?
Loss of a single chromosome
73
What is trisomy?
Gain of a single chromosome
74
What is tetresomy?
Gain of a homologous pair
75
What can cause aneuploidy?
Deletion of centromere, Robertsonian translocation, non-disjunction
76
What is autoploidy?
All chromosomes are from a single species, can arise through non disjunction
77
What is alloploidy?
Chromosomes are from two species, mostly arise from hybridisation between two species followed by chromosome doubling
78
What is a monohybrid cross?
Cross between two parents that differ in a single characteristic
79
What does gene conversion always lead to?
The death of gametes
80
What does unequal crossing over lead to?
Duplication and deletion
81
What does deamination of methylcytosine lead to?
C mutating to a T
82
What was discovered by comparing human and chimp genomes?
The human chromosome 2 is the result of a Robertsonian translocation
83
Which chromosome has the fewest trisomics?
1
84
What is Mendel's first law?
Each individual diploid organism possesses two alleles for any particular characteristic. These two alleles separate when gametes are formed and one alleles goes to each gamete
85
What is the principle of dominance?
When two different alleles are present in a genotype, sometimes only the trait encoded by one of them, the 'dominant' allele is observed in the phenotype
86
What is a backcross?
F1 is crossed to one parent
87
What is a testcross?
Individual of unknown genotype crossed to known type
88
What is a reciprocal cross?
Pair of crosses with phenotype of male and female parents reversed
89
What revealed the law of independent assortment?
Dihybrid crosses
90
What do segregation ratios depend on for two loci on the same chromosome?
The rate of crossing over between loci
91
What reveals the effect of linkage?
Testcross
92
If two genes are linked, what are all the progeny?
Non-recombinant, same as parental phenotypes
93
How can the % recombinant progeny be calculated?
#recombinant progeny/total x 100
94
What is a linkage map?
The order and distance between loci on a chromosome
95
What is distance between chromosomes measured in?
CentiMorgans, 1cM = 1% chance crossover
96
What does non-Mendelian genetics include?
Mitochondria, chloroplasts, X/Y linked
97
What is homoplasmy?
All organelles are genetically identical
98
What is heteroplasmy?
Different cells in the same organism being genetically different
99
What is position effect variation caused by?
Inversion mutation or transposons
100
What are the characteristics of cytoplasmically inherited traits?
Present in males and females
Usually inherited from one parent
Reciprocal crossed give different results
101
What do genetic maternal effects mean?
Offspring's phenotype is determined by mother's phenotype
102
What is clonal inheritance?
Means the whole mtDNA has shared history
103
What can be used as a clock to find the most recent common ancestor?
Mutation rate
104
What is gene conversion?
The process by which one DNA sequence replaces a homologous sequence such that the sequences become identical
105
When can gene conversion occur?
In meiosis, when crossing over is resolved differently
106
What is DSBR?
Double strand break repair
107
What is SDSA?
Synthesis dependent strand annealing
108
What are homing endonucleases?
Stretches of DNA that code for sequences that both copy itself and cut the unoccupied allele at the correct insertion site
109
What are B chromosomes?
Extra set of chromosomes, not stabily transmitted
110
What is meiotic drive?
Gametes produced have unequal chance to fertilise
111
What are nuclear non-Mendelian loci?
Selfish genetic elements which increase in frequency in populations quickly due to unfair inheritance
112
What are monoecious individuals?
Ones that have both male and female reproductive structures
113
What are didecious individuals?
Ones that have either male of female reproductive structures
114
What is heterogametic sex?
Produces gametes with different types of sex chromosome, eg human male XY
115
What is homogametic sex?
Produces gametes that all contain the same type of sex chromosome
116
How does haplodiploidy work in bees?
An unfertilised egg becomes a male and a fertilised egg becomes a female
117
What is genic sex determination?
Sex determining gene but no sex chromosomes
118
How is the sex of reptiles often determined?
Based on temperature
119
How is the sex of fish often determined?
They are born one sex and change based on social cues
120
What is human sex determination based on?
The SRY gene on the Y chromosome
121
What are sex limited traits
Genes present in both sexes but only expressed in one
122
What are sex biased traits?
Genes present in both but expressed more in one sex
123
What are sex linked traits?
Genes on sex chromosomes
124
How did sex chromosomes differentiate?
A mutation of a gene on one chromosome causes maleness, and mutations at other genes affect male characteristics. Suppression of crossing over keep genes fro male traits linked to the male determining gene and over time, lack of crossing over leads to degeneration of the Y
