Reproduction Flashcards
1
Q
How is sexual reproduction Expensive?
A
- Finding a mate
- Assess mate potential
- Produce gametes
- Mating
- Carry and care for offspring
- Possibility of unsuccessful mating
- Balance between parental investment & reproductive success so fewer offspring
- More complicated so higher chance it goes wrong but have more variation
2
Q
Types of Variation in Sexual reproduction
A
- Recombination
- Independent assortment
- Random fertilization
3
Q
Why is mitochondria only from the female gamete?
A
- Only the sperm nucleus enters the egg because if it let a whole cell into the egg it would also be able to let in bacteria so it only lets a part of the sperm in
- Evolution from bacteria where they transfer gene material not the whole cell
- Sexual dimorphism decreases risk of self-fertilization (natural fail safe)
- To avoid risk of infection other cells/organelles are not allowed into egg
4
Q
Advantage: group selection
A
- Greater variation
- Variety comes with the probability that some offspring will survive in a changing environment
- Ex: Irish potato famine had no variation in its crop so one virus could wipe most of the potatoes out
5
Q
Advantage: environmental effects on life history
- Asexual vs Sexual
A
- Asexual= highly variable environments
o Reproduce quickly so can survive at various environments
o Short lives to ensure reproduction
o High rate of reproduction and mutations
o Take antibiotics every 12 hours because it will kill the bacteria at its exponential stage of growth - Sexual
o Longer lives so better for stable environments because cant respond to rapid change
o Variable phenotypes ensure some success
6
Q
chromosomes
eukaryote vs prokaryote
A
- Prokaryotes: genetic material is a small circular DNA
- Eukaryotes: more genetic material organized un chromatin, which condenses in chromosomes during nuclear division
7
Q
Karyotype Test
A
- Karyotype is a test to identify and evaluate the size and shape and number of chromosomes in a sample of cells
- Karyotype analysis process
o Force cells into mitosis then stop at metaphase stage to view the condense chromosomes
o Heterochromatin: dark, condenses DNA, not expressed
o Euchromatin: light bands, expressed
8
Q
chromosome abnormalities
A
- evolutionary constraint
- Numerical abnormalities
o Written as: # of ch, sex ch, + extra, ex: 47, XY, +18
o Aneuploidy : loss or gain of 1 chromosome
o Monosomy: loss of 1 chromosome and only survivable one is Turner syndrome with one X chromosome only
o 2 types of trisomy : dosage affect prevents survival of most trisomy
1. Autosomes (21, 18, 13)
2. Sex chromosomes
-XXX: turn off 2 X - Kleinfelter: 47, XXY turn off 1 X
- Jacobs: 47, XYY has no problems with carrying to term because it doesn’t code for anything important but does seem to increase testosterone and antisocial behavior because its at an increase in prison populations
9
Q
Chromosome Abnormality in Newborns
A
- 50% of all spontaneous miscarriages have chromosomal abnormality & 80% of those in 1st trimester
- 0.5-1% live births have chromosome abnormalities
- Miscarriage is high due to the types of genes and the dosage effect
10
Q
Non-Disjunction
A
- Separation in meiosis 1 is unsuccessful leading to gametes with more and less than normal amounts of genetic info
- 50/50% chance of a trisomy or a monosomy
11
Q
Non-Disjunction and Age
A
- Older women’s chromosomes have been formed inside of them since they were born and are released when they ovulate and the longer it takes to fertilize them the longer the chromosomes will have spent being stuck together and lower the chances they will pull apart
- 90 % maternal ND because have carried eggs since their own birth
- 5% paternal ND because the sperm is on a cycle creating new ones about every 6 weeks
- 4% Robertsonian translation
- 1% mosaicism
12
Q
Robertsonian Translocation at meiosis
A
- First, they Lose short arms of 2 chromosomes and fuse together to make a new chromosome
- Now have a 14, 21, and 14/21
- 6 possible game combos where 50/50% lead to death or survival
- Outcomes lead to unbalanced genetic material
- Normal: 14, 21 (1/3 chance for the survival gametes)
- Normal carrier: 14/21 will have normal phenotype but be a carrier for Robertsonian
- Down syndrome: 14/21, 21 leads to this because get 2 copies of 21 from mom and 1 from dad during fertilization
- Lethal combos are: 14 alone, 21 alone, & 14, 14/21 which leads to a 14 trisomy
13
Q
Mosaicism
- 2 cases
A
- Presence of 2 or more cell lines with different genetic makeup in an individual
- Milder form of down syndrome because some cells in the body have Down and some don’t
- 2 cases:
1. Nondisjunction during early division after fertilization causing some cells to have trisomy and others to not
2. Start with a Down syndrome embryo where some cells revert back and lose the extra chromosome after fertilization
14
Q
Down Syndrome
A
- Trisomy of 21
- Symptoms: low IQ, behavior/cognitive retardation, congenital heart and GI tract defects, epicanthal folds, broad nasal bridge, short stature, smooth philtrum, early onset of Alzheimer’s
- Same rate of incidence in the last 100 years because of the increases in maternal age leads to an increase in non-disjunction but incidence of trisomy stays low because of abortion (we can detect early on if baby has trisomy)
15
Q
Sex Determination
A
- Organisms that have sexual reproduction usually have 2 sexes
- Many systems in nature determine the sex
1. Environmental parameters: alligators develop sex based on the temp at which they are incubated
2. XX vs XO: increase elegans, the presence of 2 copies of the sex chromosome determines a female and one sex chromosome makes a male
3. XX vs XY: humans, most mammals, some insects where XX= F, XY = M
16
Q
Barr Body
A
- Lyonization: the inactivation of the extra X chromosome into a Barr body, occurs early in embryonic development, random inactivation, inactivation is transmitted to daughter cells
- F= XX & M=XY (only 1 X)
- Inactivation of one X chromosome prevents females from having twice as many X chromosome gene products as males
- Inactivation if one X chromosome only takes place in somatic nuclei
- Ex: calico cats fur color because only females have XX
17
Q
Turner Syndrome
A
- Only monosomy compatible with life
- 45, XO (no barr body)
- Phenotypically female
- Webbed neck
- Ovarian formation failure so no period and sterile
- Short in stature because they have less SHOX genes (dosage effect)
- Normal IQ
- Impaired social cognition
- Associated disorders: renal problems, Hashimoto’s thyroiditis (autoimmune hypothyroidism), cardiac problems
18
Q
Klinefelter Syndrome
A
- 47, XXY (inactivate 1 X to limit dosage effect)
- Phenotypically male
- Learning difficulties
- Increased antisocial and criminal behavior (in XYY too)
- 50% normal fertility
- Taller than average because they have more SHOX genes in the barr body (dosage effect)
- Slightly lower IQ
19
Q
Women with XXX
A
- Low IQ
- Tall stature
- Normal fertility
- Learning disability and antisocial behavior
20
Q
Effects of Differences in Sex Development
A
- Crucial aspect of development
- Differences of Sex Development Effects
1. Congenital conditions where chromosomal, gonadal or anatomical sex is atypical (physical and genetic se don’t match)
2. Lifelong emotional and psychological consequences
3. Develop as a consequence of our evolutionary history
4. Cultural taboo/ignorance
21
Q
SRY = Sex determining region on Y chromosome
A
- M & F reproductive tracts arise from the same embryonic tissue
- If SRY is present, then Sertoli cells are expressed leading to the differentiation of Leydig cells which produce testosterone (which goes toward M formation) and inhibition of female genitalia development
- If no SRY then go to ovaries
- By default you develop F but if anything disrupts the factors in the pathways it can lead to a change in internal and external genitalia
- Q: What happens if a patient has XX but the SRY is translocated onto and an X chromosome?
A: the patient would be genetically female but would develop male sex organs
22
Q
Differences in sex development
A
- Patients that acquire mutations on the gene coding for proteins involved in sex determination
- Called XX DSD (anything but fully F) and XY DSD (anything but fully M)
- Hopefully no more gender reassignment before puberty
23
Q
2 extreme examples of differences in sex development
A
- 46 XY Complete Gonadal Dysgenesis = cant develop internal/external M genitalia
- Female appearance with normal uterus and fallopian tubes
- No ovaries
- 15-20% caused by a mutation or deletion on the SRY
- Sterile - 46, XX Gonadal Dysgenesis
- Male or ambiguous genitalia
- Translocation of SRY onto another chromosome (often the X chromosome)
- Often have Male gender identity
- Sterile
24
Q
qualities of human reproductive strategy
A
- High investment, few offspring
- Single births norm
- Infanticide of multiples (usually F)
- Factor driving offspring # is amount of resources
- 2 examples of populations with no family planning or contraceptives
1. Kung: Botswana, 4.7 births, fewer resources
2. Hadza: Tanzania, 6 births, more resources
25
Q
cost of fecundity
A
- Study of 19th century Bavarian villages
- Longer birth intervals = higher chance of survival for the younger sibling
- Which links back to amount of resources & poverty
26
Q
mate choice
A
- In males the # of offspring increases with an increase in the # of mates but not for women
- Female reproduction is more expensive than in males
- So females tend to be more selective than males about mates
- Bateman’s Principle: women are more selective than men are because reproduction is more expensive for them
27
Q
Human Male Mating strategies
A
- Goal: maximizing mating opportunities while also ensuring offspring survival
- Monogamy = ensures survival of offspring but a tradeoff with opportunity to have more offspring and mates
- Polygamy/polygyny = more offspring but tradeoff with less parental care
- Influencing factors like culture, society, religion
28
Q
Human Female mating strategies
A
- More selective (Bateman’s Principle)
- Fitness maximized by selecting a mate that can contribute to survival of offspring by having good genes, providing care, being reliable & dependable
