Selection process and Genetics Flashcards
Git gud
1
Q
What are the kinds of selections?
A
Disruptive selection, balancing selection, oscillating selection, frequency-dependent selection and directional selection
2
Q
What is the Red Queen Hypothesis?
A
There is always pressure to evolve counter-adaptations and, hence, exposed to directional selection. The continuous arms race between two parties.
3
Q
What are the two types of evolutionary change?
A
Anagenesis (micro evolution) and Cladogenesis (“branching” macro evolution)
4
Q
Explain Allopatry and Sympatry
A
A - species divergence in geographically isolated areas
S - divergence occurs in same area; time, microhabitat or behaviour
5
Q
What is Host-parasite cospeciation?
A
When both the host and parasite have a species divergence resulting in 2 new species for both.
6
Q
What is autopolyploidy?
A
Autopolyploid organisms have more than two sets of chromosomes that are from the same species
7
Q
What is allopolyploidy?
A
Allopolyploid organisms have more than two sets of chromosomes that are from different species, such as the wheat plant
8
Q
Somatic cells are…
A
Any body cells that do not produce gametes (egg or sperm cells)
9
Q
Germ cells are…
A
A diploid reproductive cell that gives rise to a gamete
10
Q
How many sets of chromosomes do diploid cells have?
A
2
11
Q
How many sets of chromosomes do haploid cells have?
A
1
12
Q
Where are genes located on a chromosome?
A
The locus
13
Q
What proteins help with the folding of DNA (wrapped around) ?
A
Histones
14
Q
What is methylation?
A
Affects how tightly coiled the DNA and effectively switches genes off?
15
Q
What are the 2 types of cell division?
A
Mitosis and meiosis
16
Q
What are the phases of mitosis?
A
prophase, metaphase, anaphase and telophase
17
Q
What are autosomes?
A
The 22 pairs of chromosomes that do not determine sex
18
Q
What is the human karyotype?
A
an ordered display of the pairs of chromosomes in a cell
19
Q
What are the two chromosomes in each pair called?
A
homologous chromosomes.. each pair carry alleles of the same genes. Each includes one chromosome from each parent
20
Q
what is the centromere?
A
The centromere links a pair of sister chromatids together during cell division
21
Q
How many chromosomes are in a human?
A
46, 23 from the mother and 23 from the father
22
Q
Where does mitosis take place?
A
In many tissues that need to replace cells
23
Q
What is cytokinesis?
A
The cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.
24
Q
What is meiosis?
A
Cell division producing
gametes each possessing the haploid number of chromosomes (n) and haploid content of DNA (c)
25
Why is meiosis necessary?
It is required to allow offspring to be produced with half of their genetic information from their mother and half from their father
26
What does 2n and 4c mean in meiosis?
2n = the number of chromosomes
4c = 4x the haploid content of DNA
26
What occurs in meiosis I?
homologous chromosomes separate.
2 haploid daughter cells are formed – Reductional Division.
26
What are the three unique events that occur in meiosis I?
-At the metaphase plate there are paired homologous chromosomes (tetrads) instead of individual replicated chromosomes.
-It is homologous chromosomes, instead of sister chromatids, that separate.
-Synapsis and crossing over: Homologous chromosomes physically connect and exchange genetic information.
26
What occurs in meiosis II?
sister chromatids separate.
4 haploid daughter cells are formed. Each with a haploid set of unreplicated chromosomes.
27
How does 'crossing over' occur?
breaking and re-joining at the crossover point the chiasma of sister chromatids
27
How does Klinefelter syndrome and Turner syndrome prove that Y may have a dominant male determining gene?
As only one Y is required to drive male gonad and genital development even in XX individuals (XXY)
27
What is eukaryotic sexual reproduction based on?
meiosis. Only eukaryotes have meiotic sex as other domains are still asexual.
28
Explain fission, budding and fragmentation in terms of asexual reproduction.
fission: division into two equally-sized offspring (sea anemone)
budding: unequal division; smaller offspring (Hydra)
Fragmentation: parent breaks off into many small new individuals (kalanchoe) (think of clippings from trees)
29
What is Daphnia (water flea) an example of in terms of reproduction?
Cyclical parthenogenesis, reproduction switches seasonally. Autumn, poorer conditions - sexual. Spring and summer - asexual in good conditions.
30
What does apomixis or parthenogenesis mean?
reproduction from an ovum without fertilisation
31
How do whiptail lizards reproduce?
Through parthenogenetic means, stimulate ovulation through pseudo-mating.
Lizard on top: estradiol low and progesterone high; small ovary
On bottom: estradiol high, ovary increase in size and ovulate
32
What does phylogeny mean?
evolutionary descent with reflected levels of genetic similarity - because of shared evolutionary histories
33
All members of one Genus..
..share a more closely related common ancestor than any member of a different Genus
34
Why do you never get a genus with all asexual species?
Because you need sex for differentiation to occur. Obligate asexual reproduction is found ONLY at the level of individual isolated species within an otherwise sexual genus, you cannot find a Genus made up of multiple asexuals due to a lack of genetic diversity. Obligate asexual organisms are therefore at an evolutionary dead end.
35
What does different sexes promote?
outbreeding and prevents 'selfing'
36
What is anisogamy?
a form of sexual reproduction wherein males and females produce sex cells, or gametes, of different sizes. Mammalian males produce small gametes called sperm while females produce larger gametes called eggs.
37
What is outbreeding?
Reproducing with another partner and not with yourself, the transfer of gametes from one individual to another, produces a genetically different individual
38
What is the R-number
Reproduction number
R of 1 - population stays the same per generation (x1) (female reproducer and male sperm provider)
R of 2 - population doubles per generation (x2) (All individuals are reproducers)
39
What was the primary drive for sexual reproduction?
To allow for diversity
40
What is SRY?
SRY gene causes maleness
Encodes a protein that is a transcription factor and regulates expression of other genes
WNT4 turns off and SRY turns on .. leading to SOX9. This results in sertoli cells which secretes Anti-mullerian Hormone (AMH). Promotes differentiation into Leydig cells. These produce testosterone.
41
What happens when WNT4 is activated?
cells differentiate into Theca and Granulosa cells which produce estradiol and progesterone
42
What is steroid hormone biosynthesis ?
enzymes catalyse conversions from cholesterol to steroids
43
What does Aldosterone manage
salt/water balance
44
What does corticosterone manage?
anti-inflammatory steroid hormone
45
what is dihydrotestosterone?
A male sex hormone which is the active form of testosterone, formed from testosterone in bodily tissue.
46
What is the development of the genital ridge?
contains somatic gonadal precursor cells.
The Germline stem cells migrate into genital ridges from hindgut. The Genital Ridges become the indifferent gonads (containing somatic gonadal and germline stem cells)
47
What are the metanephric and mesonephros kidneys?
Metanephric - persists as adult kidney
Mesonephros - embryonic kidney, distinct from adult
48
What is the cloaca?
single posterior opening - divides to create anal and urethral openings
49
What are the Wolffian and Mullerian Duct?
W - becomes the vas deferens in males, breaks down in females
M - becomes the oviduct in females, breaks down in males
50
What happens to the indifferent genitals in a male
Genital swellings fuse together – forms scrotum and penis.
Genital folds fuse to create a tube - extends the urethra.
51
What happens to the indifferent genitals in females
Genital swellings stay separate form labia majus. Genital folds – labium minus.
Glans component of clitoris.
52
Describe the process of Oogenesis
primordial germ cell in embryo differentiates -> Oogonium (stem cell) (mitotic division) -> primary oocyte (arrest prophase, onset of meiosis I) -> secondary oocyte (onset of meiosis II, first polar body) -> Ovum (occurs due to ovulation.. entry of sperm triggers completion of meiosis II) (second polar body)
-Meiosis produces single large ovum
53
Describe the process of Spermatogenesis
Primordial germ cell in embryo differentiates -> Spermatogonium (mitotic division, producing large numbers of spermatogonia) -> (differentiation and onset of meiosis I) -> primary spermatogonium(in prophase of meiosis I, 2n) -> Secondary spermatocyte (meiosis II) (n)-> Early spermatids (differentiation, sertoli cells provide nutrients) -> sperm cells (spermatozoa)
-Meiosis produces 4 tiny sperm
-Takes around 70 days but occurs daily
54
What cell kick-starts life of the new embryo?
The ovum, no paternal contribution to function as it takes time for the paternal genome to get transcribed and translated.
55
Whose mitochondria is inherited?
The maternal - paternal mitochondria is used to power sperm motility and left outside ovum
56
What are spermatogonia?
germline stem cells, proliferate (reproduce rapidly) mitosis
57
What do sertoli cells act as in Meiosis?
act as 'nurse' cells that promote spermatogenesis
58
What is the acrosome in regards to sperm?
-organelle
-surrounded by plasma membrane that breaks down when contacted with egg
-filled with hydrolytic enzymes:
digest carbohydrate bonds
digest peptide bonds
sperm receptor for egg protein
58
Describe the ovarian cycle
-Days 0-1, primary oocyte.
-Days 2-12, oocyte growth and follicle maturation
-Day 14: ovulation - meiosis I, completed, secondary oocyte released
-Days 15-26, follicle remnants develop into corpus luteum (progesterone & estradiol)
-Day 28, corpus luteum breaks down (loss of progesterone and estradiol) (period)
59
What is capacitation in regards to sperm?
occurs in female tract as sperm swims out of seminal fluid into female tract secretions.
Acrosome membrane fuses with sperm cell membrane.
Exposes sperm receptor for egg protein
'primed' ready to fuse with egg..
60
What is the role of cortical granules?
fused to plasma membrane, releasing enzymes. Alters zona pellucida and destroys sperm receptors and prevents polyspermy (Multiple sperm fertilisation)
61
What is the blastocyst?
~6-day old human embryo
has inner cell mass and a trophoblast which is the outer layer of cells which does not contribute to embryo, only placenta
62
What does the trophoblast do?
Secretes enzymes - breaks dow molecules in endometrium allowing the blastocyte to invade endometrium. Trophoblast proliferates into endometrium. The inner cell mass forms two layers - epiblast and hypoblast
-Also secretes human chorionic gonadtropin (hCG). Maintains the corpus luteum which continues to secrete estradiol and progesterone. Maintains endometrium (no menstrual bleeding) hCG is used in common pregnancy tests. -> Corpus luteum degenerates
63
Describe the process of the Blastula Aquatic embryos
Fertilization is followed by cleavage, a period of rapid cell division without growth
Cleavage partitions the cytoplasm of one large cell into many smaller cells called blastomeres (early blastula are totipotent)
The blastula is a ball of cells (blastomeres) with a fluid-filled cavity called a blastocoel
64
What is the amnion?
a fluid-filled sac surrounding the embryo, same salt concentration as the ocean as terrestrial life evolved from aquatic life and has to replicate the conditions.
65
Affects of pregnancy on immunology ?
The regulation of the immune system is significantly altered during pregnancy to prevent rejection
sufferers of various autoimmune diseases experience remission.
66
Describe the human prenatal development
Day 1 - Fertilisation in oviduct – cleavages (early cell divisions) start.
Day 4 – embryo gets to the uterus.
Day 7 – ball of cells with cavity – blastocyst.
Day 12 – implanted into endometrium of uterus
Weeks 2–4 nutrient directly from endometrium. Differentiation & development starts.
Week 5 – placenta developed – makes estrogen and progesterone.
Week 6-7 sex determination.
End of 1st trimester most development and organogenesis complete – 5cm long.
2nd and 3rd trimesters – mostly growth, movement and preparation for birth.
38 weeks after fertilisation – birth.
67
terminally differentiated
fixed single cell type like muscle cell
68
Morphogenesis
generation of shape, pattern and form
69
What are monoblasts ?
only one layer blast cells (a type of pleuripotent stem cells in the early embryo). no true tissues. eg. sponges
70
What are diploblasts?
Only two layers blast cells. A digestive cavity. this has one opening, which serves as both mouth and anus plus 2 or 3 related HOX genes. e.g. jellyfish
71
What are triploblasts?
Three layers of embryonic blast cells- each layer restricted to different future potentials. A mouth, anus and a gut in-between. e.g. flies and humans
72
What is gastrulation?
A movement and reorganisation of cells that is linked to creation of three fundamental layers of blast (or stem) cells in the early embryo - termed ectoderm, mesoderm and endoderm which have different restricted pluripotencies
73
What are bilateria?
triploblastic bilaterally symmetrical. Have a mouth, anus (anterior/posterior) and a gut in-between. They also have left/right symmetry (dorsal/ventral). At least 7 HOX in earliest bilaterian.
74
What do endoderm germ layers form in vertebrates vs insects
vertebrates - gut, liver, lungs
Insects - gut
75
What do mesoderm germ layers form in vertebrates vs insects ?
Vertebrates - skeleton, muscle, kidney, heart and blood
Insects - muscle, heart, blood
76
What do ectoderm germ layers form in vertebrates vs insects
vertebrates - skin and nervous system
Insects - cuticle and nervous system
77
What do homeotic genes encode?
transcription factors.. specify regional identity to body segments
78
What is the Hox gene cluster(s)?
a cluster of related homeotic genes
79
What does the expression of HOX proteins provide?
a global positioning system giving regional identity in animals
80
How many Hox clusters are present in mammals?
4
81
What is Synpolydactyly
a genetic condition caused by a mutation in the human homeotic gene HOXD13. Repeated thumb
82
What is the Cambrian explosion of the bilateria?
When a sudden radiation of complex life occurred and practically all major animal phyla started appearing in the fossil record.
