Module 3 - Genes Flashcards
(121 cards)
1
Q
what is asexual reproduction?
A
a single organism creates a genetically identical copy of itself
2
Q
in what type of environment is asexual reproduction advantageous?
A
stable environments
3
Q
what are they types of asexual reproduction?
A
- budding
- fragmentation
- fusion
- gemmulation
- regeneration
- self-fertilisation
- poarthenogenesis
4
Q
what is budding?
A
new organisms grow from parents
5
Q
what is fragmentation?
A
parents splits into uneven parts, each forming a new individual
6
Q
what is fusion?
A
parent splits into two equal parts
7
Q
what is germmulation?
A
cluster of totipotent cells protected inside pparent, can hatch later
8
Q
what is regeneration?
A
lost body parts can regrow
9
Q
what is self-fertilisation?
A
individuals can fertilise its own eggs
10
Q
what is parthenogensesis?
A
produces eggs that do not need fertilisation
11
Q
what is sexual reproduction?
A
requires two sex cells to comine their genetic material
12
Q
why is sexual reproduction beneficial?
A
genetic recombination increases cariation, which is useful in changing environments
13
Q
how do gametes contribute to sexual reproduction?
A
gametes carry hald a genome and fuse to form a new organism
14
Q
who discovered differences in chromosome number in Ascaris cells?
A
Edouard Vasn Beneden (1883)
15
Q
what did Vans Bendeden propose about gametes?
A
gametes have half the normal chromosome count
16
Q
what happens to gametes during fertilisation?
A
gametes fuse to form a zygote (precursor to embryo)
17
Q
whta is the purpose of meiosis?
A
reduces chromosome number in cells by half to form gametes
18
Q
what happens during interphase in meiosis?
A
DNA replication occurs (2n)
19
Q
what occurs in meiosis I?
A
- prophase I: homologous chromosomes pair (synapsis)
- crossing over: exchange of gentic material (4 uniquie chromatids)
- metaphasse I: chromosomes line up randomly
- anaphase and telophase I: centromere does not divide, forming haploid cells (1n)
20
Q
how is meiosis II different from meiosis I?
A
- meiosis II is similar to mitosis, resulting in 4 haploid cells
- meiosis I reduces the chromosome number by half, separating homologous chromosomes, while Meiosis II separates sister chromatids, resulting in four haploid cells with non-duplicated chromosomes
21
Q
whwere does meiosis occur?
A
only in germ cells during gametogenesis
22
Q
what is the difference between spermatogenesis and oogensesis?
A
spermatogenesis: forms 4 sperm cells
oogenesis: forms 1 egg and 3 polar bodies
23
Q
where does spermatogenesis occur?
A
in testes, specifically in semiinferous tubles
24
Q
how oftern does spermatogenesis occur?
A
continuously
25
where does oogenesis begin?
in the embryo
26
what happens to oocytes before puberty?
they pause at prophase I until puberty
27
when does meiosis resume in females?
at piberty during menarche, one primary oocyte resumes meiosis
28
where does oogenesis pause again?
metaphase II, until fertilisation occurs
29
how does meiosis create genetic variation?
1. intrachromosomal recombination; crossing over during prophase I
2. random distribution of chromosomes; anaphase I
3. mixing of parental genomes; occurs at fertilisation
30
why is sexual reproduction beneficial?
generates new genomes suited for changing environments
31
how does asecual reproduction introduce genetic change?
through mutation
32
what is a genotype?
the genetic arragemeny of alleles in an orgainsms chromosomesw
33
what is a phenotype?
they physical, behavioral, and physiological traits of an organism
34
how does the environment affect phenotype?
when the same genotype produces different phenotypes depending on environmental condiations, called phenotypic plasticity
35
what does pure breeding mean in garden peas?
offspring are gentically identical to parents due to self-fertilisation
36
how does self fertilisaiton occur?
male gametes fertilise female gamets from the same individual
37
who discovered the basic principles of genetic inheritance?
Gregor Mendel
38
what determines seed colour in peas?
an inheritable factor with two forms:
1. dominate Y, yellow
2. recessive y, green
39
how does seed colour inheritance work?
each plant passes one one form of the trait to each gamete with equal probability
40
what does Mendel's first law state?
the two alleles of a gene segregate during gamete formation, so half of the gametes carry one allele and half carry the other
41
when do alleles rejoin?
randomly during fertilisation
42
what is incomplete dominance?
a blend of parental phenotypes
eg. RR (red) x rr (white) --> F1 (pink, Rr)
F2 ratio: 1:2:1
43
what is co-dominance?
both traits appear separetely in offspring
eg. Rr (red and white stripes)
F2 ration: 1:2:1
44
what is a test cross?
crossing an individual with a dominant phenotype to a recessive homozygote too reveal its genotype
45
what are examples of two-trait inheritance in peas?
yellow and round (dominant)
green and rough (recessive)
46
what is the expected F2 ration in a dihybrid cross?
9:3:3:1
47
what does Mendel's second law state?
the segregation of different allele pairs occurs independently
48
what is a two-point test cross?
crossing a double heterozygote to a double recessive homozygote to study gene linkage
49
what is the chromosome theory of inheritance?
genes are carried on chromosomes (Sutton, 1902)
50
how is genetic information organised on chromosomes?
chromosomes contain genes
each gene consits of loci
each locus holds one allele
51
how many alleles does a diploid organism have at each locus?
two, one from each parent
52
what happens to chromsomes during meiosis?
chromsomes duplicate before division
homologous alleles can swap at equivalent loci through recombination
53
what determiens biological sex inheritance?
autosomes are indentical in males and females
sexchromosomes
54
what are some exceptions to mendelian genetics?
1. continious variation: many genes influsce a single trait
2. pleiotropy: one gene affects multiple traits
3. more than two alleles
4. epistasis: one genes effect depends on another genes presence
5. phenotypic plasticity: different environments express different phenotypes
55
what is epistasis?
the interaction between genes where one influces anothers expression
eg. labrador coat colour (9:3:4)
56
what is evolution?
change in the genetic composition of a population across generations
57
what are the two scales of evolution?
microevolution: genetic changes within gene pools
macroevolution: large-scale changes, such as formation of new species
58
what are the two main components of Darwin's theory of evolution?
- descent with modification: organisms change over generations
- natural selection: drives evolutionary change
59
does natural selectrion always lead to evolution?
no
60
what is required for descent with modification?
pre-existing genetic variation
61
how does Mendelian genetics relate to evolution?
it predicts the proportion of different genotypes in offspring, though unexpected mating can still occur
62
what is genotypic frequency?
the proportion of individuals in a population with a specific genotype
63
what is allelic frequency
the proportion of each allele within the gene pool
64
what are the five assumption of Hardy-Weinberg equilibrium?
1. random mating
2. no mutation
3. no migration
4. no natural selection
5. large population size
65
what happens of all HWE assumptions are met?
1. allelic frequencies remain constant over time
2. genotypic frequencies stabilise after one generation at the proportions P^2 + 2pq + q^2
66
what is assumptions are not met?
evolutionary forces are likely acting on the population
67
what is positive assortative mating?
individualsa perfer mates similar to themselves
68
what is negative assortive mating?
individuals prefer mates that are genetically different
69
what is inbreeding?
a form of positive assortive mating where relatives mate, including self-fertilisation
70
how does non-random mating affect allele frequencies?
it changes genotypic proportions but not alter allele frequiencies
71
how do mutation contribute to evolution?
mutations introduce genetic variation, individual mutations are rare
72
what effect does migration have on populations?
more genetically similar, reduces divergence between populations, maintains genetic variaiton
73
what is genetic drift?
random changes in allele frequencies from one generation to the next due to change
74
what factor affects rate of genetic drift?
smaller populations - greater fluctuations
75
what is fixation in genetic drift?
when only one allele ramains in the popualtions and others are lost
76
how does genetic drift impact conservation genetics?
causes loss of genetic variation in small popualtions
77
what is the only mechanism that causes adapative change?
natural selectin
78
what conditions are needed for natural selection?
variation, traits inherited from parents, differential survival and reproduction
79
what are two types of sexual selection?
1. intrasexual competition: individuals comptet for mates
2. intersexual choice: one sex selects mates based on traits
80
what are benefits of mate choice?
resources, shelter, protection
81
what are indirect benefits of mate choice?
offspring inherit advantageous traits
82
what is the morphological tazonomic species concept?
species are defined based on physical similarities
83
what is the evolutionary species concept?
a species is a lineage of populations with a common ancestry, remaining distict from other species
84
what is the ecological species concept?
a species constists of individuals sharing ecological attributes
85
what do all species concepts have in common?
restriction of gene flow
86
how does Mayr define a species?
groups of interbreeding individuals reproductively isolated from others
87
what are limited of this concept (biological species concept)
- does not inclue asexual species or fossils
- overlooks hybridisation
- morphological diversity does not align with reproductive isolation
88
what are two things required for speciation?
divergence and reproductive isolation
89
what is allopatry?
populations do not overlap geographically
90
what is sympatry?
populations occur in the same place
91
how doe sysmpatric speciation differ from allopatric speciation?
new species arise without a geographical barrier
92
what are the two types of reproductive barriers?
post-zygotic and pre-zygotic
93
why can post-zygotic barriers not be direcly selected for?
natural selection cannot facour inviable offspring
94
what causes post-zygotic barriers?
incidental genetic changes (ie. genetic drift, mutation)
95
what are examples of post-zygotic barriers?
zygote dies early, hybrids survive but are sterlie
96
what is reinforcement in pre-zygotic isolation?
slection favors mechanisms that prevent maladaptive hybrids
97
what are examples of pre-zygotic barriers?
ecological, temporal, behavioural, mechnical, gametic
98
what is adaptive radiation?
rapid diversification of a single lineage
99
how does adaptive radiation affect species?
increases morphological and ecological diversity
100
what is character displacement?
species develop accentuated differences in region where they co-exist
101
why is meiosis necessary for sexual reproduction?
ensures that gametes are haploid, preventing doubling of chromosome number in each generation
102
what happens to somatic cells and gametes during meiosis?
remain diploid, gametes undergo meiosis do become haploid
103
what is syngamy?
fusion of two hapolid gametes to form a diploid zygote
104
what are germ-line cells?
cells set aside to undergo meiosis and produce gametes
105
how do somatic (diploid) and germ-line cells (haploid) differ in division?
somatic cells undergo mitosis
germ-line cells undergo meiosis
106
what happens during prophse I?
homologues chromoesomes pair up in a process called synapis, crossing over occurs, DNA coils tightly, synapse
107
what is the synaptomenmal complex?
a protein structure that joins homolohous chromsomes during prophase I
108
what is a tetrad or bivalent?
a paired set of homologous chromsomes
109
how does crossing over occur?
homologues exchange genetic material at chiasmata during prophase I
110
why is there crossing over?
increases genetc diversity
111
what are recombination nodules?
enzymatic structures that facilitate breaking and rejoing chromatids during crossing over
112
what happens during meiosis II?
sister chromayids separate, similar to mitosis without further reducing chromosome number
113
why is monopolar attachment of kinetochores important in meiosis I?
ensures homologues, not sister chromatids, separate correctly
114
what happens during anaphase I?
spindle fibres shorten, pulling homologues to opposite poles
115
what is the key difference between meiosis and mitosis in anaphase I?
homologues separate not sister chromatids
116
what happens during telophase I?
nuclear membranes re-form around each haploud daughter nucleus
117
why are sister chromatids no longer identical after telophase I?
crossing over in prophase I
118
what is aneuploidy?
gametes have extra or missing chromosomes
119
what is nondisjuction?
failure of chromsome separation, producing gametes with too many or too few chromosomes
120
what is disjuction?
normal chromsome separation during anaphase I and II
121
what are the four features that distinguish meiosis from mitosis?
1. homologous paring and crossing over in meiosis I
2. sister chromatids stay together in AI
3. sister kinetochores attach to same pole in meiosis I (mitosis is opposite poles)
4. DNA replication is suppressed between the two meiotic divisions
