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heredity Flashcards

1
Q

pure stains

A

plants when self fertilised prod progeny (offspring) that resembles parents

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2
Q

pure bred plants

A

plants self fertilised prod progeny w same characteristics

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3
Q

monohybrid cross

A

cross in which 2 parents differ in oni 1 pair of characteristics

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4
Q

hybrid

A

offspring form 2 diff varieties of same species/ 2 diff species

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5
Q

phenotype

A

observable / expressed traits in org

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6
Q

genotype

A

genetic makeup of org (TT, Tt)

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7
Q

allele

A

may be diff in homologous chromo (alt forms of the same gene that occupy same relative position on a pair of homologous chromo)

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8
Q

what makes up a genetic diagram (in order)

A
  • parents phenotype
  • parents genotype
  • gametes
  • F1 genotype
  • F1 phenotype
  • phenotypic ratio
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9
Q

every female has

A

22 pairs of autosomes, 1 pair of XX chromo (all eggs have X chromo)

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10
Q

every male has

A

22 pairs of autosomes, 1 pair of X or Y chromo (half the sperms carry X, other half carry Y )

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11
Q

gender of offspring determined by… and why?

A

male

  • equal chance of egg being fertilised w sperm with X or Y chromo = equal chance of baby being girl or boy
  • might not always be true bc observed ratio differ form expected when there is small no of progeny
  • gametes unite at random
  • result of fertilisation independent of earlier outcome
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12
Q

law of segregation(Mendel’s 1st law)

A
  • the characteristics of an organism r controlled by genes occurring in pairs
  • of a pair of such genes, only one gene can b carried in a single gamete
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13
Q

naming of trait

A

always the 1st letter of the trait(except for universally accepted ones like bld grp & the recessive trait–> small letter)

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14
Q

magic ratio for phenotypes

A
  • 3 dominant trait: 1 recessive trait –> hetero x hetero
  • all offspring show dominant trait–> one of the offspring MUST b homozygous dominant–> homodom x homorec
  • -> homodom x heterozygous
  • ->homodom x homodom
  • 1 dominant trait: 1 recessive trait–> hetero x homorec
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15
Q

test cross

A

a cross btwn organism showing the dominant trait w an organism that is homorec

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16
Q

pedigree chart

A

a collection of info abt a famiy’s history/pedigree for a particular trait

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17
Q

codominance

A
  • results whn the 2 alleles controlling a trait both expresses themselves in the organism-
  • neither alleles of a gene is dominant over each othr
  • both alleles express themselves in the hetero conditions such that the offspring has phenotype intermediate btwn that from the 2 homo conditions
  • represented by 2 diff capital letters or a common letter w 2 diff capital superscripts
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18
Q

multiple allele inheritance

A

multiple allele is a term used for a gene that exists in more than 2 alleles
eg bld grp A–> IAIA, IAIO
B–> IBIB,IBIO
AB–> IAIB
O–> IOIO
the A,B,O are all superscripts
no such thing as allele that is dominant or recessive!!

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19
Q

format for answering pedigree chart qns

A

describe the phenotype of the “clue” & describe it’s genotype
use either 1. the parent has passed on ___ allele for the ____ trait
2. the child has inherited ____allele for the trait–> describe the genotype of the and(types of alleles)

20
Q

when you have both parents that have the same trait produce a kid that has a diff trait

A

this trait is recessive and was hiding in ur parents

21
Q

what is sickle-cell anaemia

A

results frm a gene mutation caused by a recessive allele which causes the rbc to b no longer circular biconcave

22
Q

when do u express sca

A

whn ur homorec, HbSHbS

23
Q

what happens whn u hv sca

A

the gene which codes for normal haemoglobin(HbA) undergoes a sudden change in the gene(gene said to b mutated–> means that nucleotide change so mRNA sequence also changes & diff amino acids)–> mutated gene is recessive & expresses itself only in the homorec condition–> HbSHbS
so ppl who r homorec hv abnormal haemoglobin(HbS) in their rbcs, HbS molecules clump tgthr making the RBCs sickle-shaped

24
Q

whats wrong w sickle shaped rbcs

A
  • can clog bld vessels & deprive the body’s tissues & organs of oxygen that thy need to stay helathy–> fatal
    (bcos bld vessels r narrow, normal rbcs r elastic & can change shape to enter narrow bld vessels but sickle-shaped rbcs cannot change shape anymore so thyll clog up the bld vessel)–> respiration rate goes down–> less enerfy–> more tired
  • unlike normal rbcs that last abt 4 months in the bloodstream, fragile sicklce cells brk down aft oni abt 10-20days, which usually causes ANAEMIA
  • sca is a nearly lethal condition in humans, reps for abt 100000 deaths a yr
  • abt 80% of indivs w this condition die b4 reproducing
25
sca in a malaria-prevalent context
- normal bld(AA)--> produces normal RBCs--> not protected from malaria(selected against), bcos when the mosquito bit u & malaria parasite enters ur bld stream since the normal rbc can last for 4 months --> it can burst thru & infect other cells but since the sickle-shaped one has a shorter life-span--> can oni reproduce a few times b4 it dies in 10-12 days - Normal hetero (Aa)--> carrier, may produce RBC which r normal or sickle-shaped(sm biconcave, sm sickle-shaped)--> protected from malaria(selected for) - sca(aa) --> all rbc r sickle-shaped, normally die b4 adulthood, not able to repro & pass on the rec allele to future generations--> so by right shld b protected from malaria but still selected against THEREFORE, being a person w normal phenotype(AA genotype) is not good if ur living in a malaria-prevalent place bcos u may suffer from the full effect of malaria ut being a person diagnosed w sca is not good either bcos u may suffer from the full effect of sca
26
sca allele is recessive in which case and codominant in which case?
it is recessive whn it cms to inheriting disease | it is codominant when it cms to inheritance of biconcave rbc shape(which is why hetero hv sm rbc which r sickle shaped)
27
what causes variations
- crossing over during meiosis = genetic variation in gametes - IA = genetic variation of chromo - crossing diff varieties of plants and animals - fertilisation , random = genetic variation bw offspring (not gamete cos gametes have alr been made) - mutation
28
causes of mutation
exposure to mutagens - radiation (UV ray, X ray, alpha beta gamma rays - chemicals (mustard gas ,tar , formal dehyde - cigar smoke) - errors in DNA replication (+ intro of parasite/ virus)
29
what is mutation
- sudden random change on structure of a gene / chromo - any change = adverse effect on the cell (formation of new alleles, new varieties of offspring , more diversity within species - occurs in normal body cells = cancers (cant be passed down to offspring) - occurs in gametes = down syndrome, albinism & accelerated aging can be passed down to offspring
30
tumour
- cancerous cells --> damaged cells dividing uncontrollably --> dont destroy themself - phagocytes cant engulf and injest - suppresor genes --> protective genes that limit cell growth (but having the gene doesnt mean its expressed)
31
downs syndrome
- inherited form of mental illness & phy retardation - form chromo mutation (ovum w xrta chromo = child w 47 chromo interferes w normal brain + body + development of child = shorter lifespan) - as mental age increases, incidents/ chances of child w downs syndrome increases bc ova of mom is made since her birth so dna quality reduces w age - fathers age cant be a factor bc sperms are fresh
32
why is mutation good
- mutation produce new alleles of a gene which increases variation within a species(make a new allele off the same genes) - occasionally mutation can happen and give the mutant organism an advantage thus it can survive to pass its new characteristics on to the next generation. the mutant may even replace the normal form obr a period of time. ---> sm indivs will leave more offspring than indivs w/o the beneficial mutation as a result, tje frequency of the mutant allele will ↑ into popz of organisms & as such changes take place, organisms w new traits may arise aft many yrs, giving rise to a new species--> nature 'selects' these organisms w more favourable traits to survive & reproduce
33
what are variations
differences in traits btwn indivs of the same species
34
discontinuous variation
- variations which take the form of clear-cut phenotype w no intermediate forms btwn the extremes - variations under the control of 1 or a few genes - characteristics remain relatively unaffected by the evco-->(eg:cannot change ur bld grp or gender by altering ur diet)
35
eg of discontinuous variation
- ability or inability to roll tongue - wings in fly - bld grp - tall or dwarf in plants - attached or detached earlobes in man
36
Artificial selection vs natural selection
AS - from manupulation by hoomans - hoomans select org with desired traits to repre - relatively faster - advantageous to man NS - from mutaton in genee - brought abt by envi process - v slow process - advantageous/ harmful to man
37
eg of continuous variation
- weight of man - footsize -height: thr may b 5 pairs of genes for height, a person who inherits more dominant allele--> taller than one who has fewer dom alleles , ovr 400genes controlling it so its vry diff to predict the height tht an off offspring will hv) or the more gene for dark skin--> more melanin u make--> more dark ur skin(the more u hv, the gr8er the effect it adds on ech othr)
38
eg of envo affecting continuous variation
exposure to sunlight-> darker skin colour or person may inherit genes for tallness but still not grow tall due to poor nutirition
39
step 1 of natural selection ( how variation? how green beetles can have brown kids hmm...)
- indivs within a species r slightly diff bc of variation - meiosis (prophase 1) - mutation (metaphase 1) - fertilisation (random)
40
step 2 of natural selection (FigHT fIGht, go court and ...)
- comps among diff varieties as resources are ltd - changes in envi, some varieties btr adapted (can survive) - selected by pressures of envi, others selected against
41
step 3 of natural selection (b4 exploding u needa let it gooooooo wht am i saying... )
- diff repro of diff varieties - envi cant support unltd pop growth not all indivs get to repro to full potential - more advantageous traits lives longer - prod more offspring
42
step 4 of natural selection (ofc u will want to eat better mangoes right)
- over time beneficial genes accumulate - new varieties more adapted to envi change - outnumber and replace OG
43
what is evolution
- nature selects those varieties tht r more competitive, more resistant to disease & better adapted to changes in the envo to reproduce - aft 1000s of yrs, w many rounds of mutations & natural selection, more beneficial qualities may acc in a species--> better fitted to the envo - the new breed of organims may change so much tht thy bcome a new species which differ frm the orginal stock frm which thy hv evolved--> better adapted to changes in the envo
44
Artificial selection
- from manupulation by hoomans - hoomans select org with desired traits to repre - relatively faster - advantageous to man
45
inbreeding
can result in the accumulation of recessive alleles in the popz eg: in the case of sca, normally if ur in a 1st-world country n ur a carrier, the chance of u meeting anothr carrier is low but in 3rd world country HbSHbA x HbSHbA--> the chance for this to happen ↑ cos the popz is vry small so chance of ur offspiring getting sca is ↑ cos the chance of mating/breeding w anothr carrier is vry high - the recessive genes tht r not expressd in the hetero parents--> more likely to b passes down to offspring--> if rec gene codes for a genetic disease, homorec offspring will suffer frm the disease - continuous inbreeding & selective breeding of particular genes runs the risk of losing sm of the othr genes frm the gene pool altogether--> irreversible - in the long termm, more advantageous for organisms to remain hetero
46
hybridisation
crossing of diff varieties(of plants) to produce a new and better variety

Biology (5 decks)

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