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PATTERNS OF INHERITANCE Flashcards

1
Q

what is phenotype and what can affect it?

A

is our appearance and it can be affected by genetic and environmental factors

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2
Q

what are mutagens and what are the types?

A

can cause mutations
-physical
-chemical
-biological
can be carcinogens

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3
Q

list physical mutagens and what do they cause

A

x-rays
gamma rays
UV light
breaks DNA strands

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4
Q

list chemical mutagens and what do they do

A

benzopyrene
mustard gas
nitrous acid
aromatic amines (synthetic dyes)
reactive oxygen species
colchicine
change one base into another

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5
Q

list biological mutagens and what they do

A

some viruses (insert viral DNA into host cell)
transposons (A transposon is a segment of DNA that has the ability to move from one genetic location to another.)
food contaminants (mycotoxin form fungi)

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6
Q

what can mutations be?

A

harmful, dangerous and neutral

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7
Q

type of mutation?

A

small-scale (gene mutations)
large-scale (chromosome mutation)

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8
Q

define gene mutation

A

changes to the base sequence within a gene

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9
Q

define chromosome mutation

A

changes to the structure or number of whole chromosomes

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10
Q

what does mutation during gamete formation cause?

A

persistent (can be transmitted
to offsprings) and random mutation (not due to the need of the part of the organisms where he mutation occurred)

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11
Q

type of chromosome mutations

A

deletion - loss of part of chromosome
inversion - section rotates by 180 degrees and then join again
translocation - piece breaks and attaches somewhere else
duplication - overexpression of genes , ca be harmful
non-disjunction - chromatids fail to separate , so there is an extra
aneuploidy - abnormal number of chromosomes , can lead to down syndrome , trisomy of chromosome 21
polyploidy - having more than 2 complete sets of chromosomes (heritable), this occurs hen a diploid gamete fertilised a haploid gamete.

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12
Q

what causes genetic variation?

A

sexual reproduction during meiosis
- independent assortment of chromosomes in metaphase and prophase 1
-independent assortment of chromosomes in metaphase and prophase 2
- allele shuffling

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13
Q

what can variation be?

A

caused by environmental factors, not due to genetic factors (losing a limb, dialect) =, not transmitted to offspring

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14
Q

what does genetic expression depend on?

A

environmental factors : environmental condition can affect the expression of genes, eg having the gene to make chlorophyll but not being able to make it due to low light intensity and soil insufficient magnesium
prevents expression of genes.

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15
Q

what is a MONOGENIC INHERITANCE?

A

where one phenotypic characteristic is controlled by a single gene

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16
Q

what are the alternative forms of gene called and what do they do?

A

alleles - give rise to differences in inherited characteristic

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17
Q

dominant vs recessive allele vs codominant

A

dominant decides what characteristic will be expressed in the phenotype, always expressed
recessive alleles are weaker so both recessive alleles are required in order to display the recessive allele characteristic
codominant alleles both contribute (so equally dominant) to the phenotype eg. cat fur or AB blood group

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18
Q

write the symbols used to describe :
HOMOZYGOUS DOMINANT
HOMOZYGOUS RECESSIVE
HETEROZYGOUS

A

BB
bb
Br

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19
Q

what is meant by dihybrid inheritance?

A

the inheritance of two trait, from 2 different genes and from different chromosomes

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20
Q

what are dihybrid crosses used for?

A

to investigate the simultaneous inheritance of 2 different characteristics (eg heigh and eye colour)

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21
Q

who was the first person to investigate dihybrid crosses? explain the experiment.

A

Mendel - he used 2 TYPE OF PURE BREEDING SEEDS : ROUND YELLOY (RRYY) AND WRINKLED GREEN (rryy) and cross breeder them using punnet square.

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22
Q

what is meant by multiple alleles?

A

when a gene has 2 or more alleles , a phenotype caused by multiple alleles due to multiple allele inheritance

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23
Q

what’s an example of multiple alleles?

A

blood group : A,B,AB, O

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24
Q

by what pair of chromosomes is sex determined?
what are these chromosomes called?

A

23rd pair - sex chromosomes

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25
what are the other 22 chromosomes knows as?
AUTOSOMES - are fully homologous
26
what is autosomal linkage?
2 or more genes are located on the same autosome (non-sex chromosome). The 2 genes are less likely to be separated during crossing over, resulting in the alleles of the linked genes being inherited together.
27
what are linked genes?
all genes located on the same chromosomes
28
what are 3 examples of sex-linked characteristics?
HAEMOPHILIA A and colour blindness
29
if a female has one abnormal allele on one of her X chromosome, she will probably have a functioning allele of the sam gene on her other X chromosome. If a male inherits, from his mother, an X chromosome with the abnormal allele for a particular gene, he will suffer from a genetic disease as he will not have a functioning ally for that a gene since he doesn't have another X chromosome
30
explain haemophilia A
genetic disease that prevents blood to clot fast enough to avoid extreme bleeding, therefore injuries may cause extreme bleeding and internal haemorrhage
31
what cause haemophilia a?
a gene (factor 8) that codes for a blood-clotting protein is found on the sexual chromosome X. A mutated form of this allele can cause a non-functioning factor 8. if a female has an abnormal allele for this gene on her x chromosome and one functioning on the other, she will sit be able to clot her blood fast enough, HOWEVER, SHE IS A CARRIER OF THIS DISEASE. if the mother passes the X chromosome with the faulty allke to her son, he will suffer from haemophilia A as he will not have a functioning allele for it on the Y chromosome
32
A mother always passes an X chromosome onto her offspring, but a father can pass on either an X or a Y chromosome. If he passes on his X chromosome, their baby will be genetically female. Biologically female people inherit an X chromosome from their father, and the other X chromosome from their mother. Biologically male people always inherit their X chromosome from their mother.
33
explain what is colour blindness
inability to distinguish between red and green.
34
what causes colour blindness
one of the gene involved in coding for a protein involved in colour vision in on the X chromosome, not on Y chromosome a mutated allele for this gene may cause colour blindness. a female with an abnormal allele for this gene will have a functional allele for the gene on the other X chromosome, However if a male inherits the abnormal allele of the gene he Weill suffer from red-green colour blindness as he doesn't have a functioning gene on the Y chromosome
35
what is X inactivation?
-when an X chromosome in females is switched off, compacted in a BARR BODY. -Most of the genes on the Barr body are inactive, meaning that they are not transcribed. -the level of gene activity produced by a single X chromosome is the normal "dosage" for a human. -Men have this dosage because they only have one X chromosome. -Women have the same dosage for a different reason: they shut down one of their two X chromosomes in a process called X-inactivation. -X-inactivation is a random process that happens separately in individual cells during embryonic development. One cell might shut down the paternal X, while the other cell might shut down the maternal X instead
36
what is codominance?
when both gene present in the genotype of a HETEROZYGOUS individual contribute to individual phenotype
37
what's sickle cell anaemia caused by?
mutation in the genes that codes for the b-globin chain of haemoglobin.
38
what is heterozygous individuals blood composed of?
have half of their bc abnormal, and half of their rbc abnormal, carry sickle cell anaemia, symptomless
39
what is epistasis?
interaction between 2 non-linked genes (2 different pair of homologous chromosomes) which causes one gene inhibiting the expression of the other gene in the phenotype
40
what is meant by epistatic genes?
the gene the is suppressing another gene
41
what are two ways in which epistatic genes can function/ work?
antagonistically - one gene suppresses / inhibits the expression of the other gene complementary fashion - one gene encourages the expression of the other gene, two genes work together
42
what is an hypostatic gene?
the gene which is being suppressed
43
what s antagonistic epistasis?
when a gene suppresses the other
44
what are the two types of antagonistic epistasis?
dominant - presence of a dominant allele in the epistatic genes prevents the expression of the hypostatic gene (1 dominant allele is enough to inhibit the expression ) recessive - presence of two recessive alleles at the first locus prevents the expression of another allele at second locus, in order to suppress th either gene, both must be recessive
45
what is variation caused by?
interaction between genetics and environment
46
what is interspecific variation?
differences between 2 or more species
47
what is intraspecific variation?
differences WITHIN THE SPECIES
48
what will high genetic diversity in a population cause?
high diversity
49
types of variation
continuous - there are 2 extremes and a full range of values between them (e g height and antigens on cell membrane) discontinuous- traits that have have distinct categories with no intermediate values (e g ear lobes , gender, blood group)
50
what are continuous variation traits caused by?
polygenic = many genes are involved in determining these traits, allele of each gene contribute a small amount to the phenotype , each allele has an ADDITIVE EFFECT.
51
what are discontinuous variation caused by?
monogenic = single gene and allele involved in determining these traits
52
does the environment has a greater effect of monogenic or polygenic characteristics?
polygenic characteristic (eg height and intelligence)
53
what are selection pressures?
environmental factors that a affect the chance of survival of an organism
54
what is natural selection?
the process by which better adapted organism survive and reproduce
55
what are the 2 types of selection?
directional and stabilising
56
what is "stabilising selection"?
natural selection that leads to constancy within a population , where extreme phenotypes are selected against/ removed and intermediate phenotypes are favoured stabilising selection reduces genetic variation within the population occurs when environment remain unchanged
57
what is directional selection?
produces a gradual change in allele frequencies over several generations natural selection that occur when an environmental change favours a new phenotype and so results in a change in the population mean occurs when the environment changes used by plant and animal to produce desirable traits
58
what is genetic drift?
when a change affects which individuals in a population survive breed and pass on they genes, change majorly affects small populations due to having a genetic variation in the population - gradual change in alleles in a small population due to chance
59
what can cause genetic drift?
genetic bottleneck or founder effect
60
what is genetic bottleneck?
sharp reduction in size of a population due to environmental catastrophes which reduces genetic diversity , as population expands it is less genetically diverse than before population size shrinks and then increase again
61
what is the founder effect?
when a small number of individuals from a large population start a new population , this leads the new population to have only some of the total alleles present in the large population - which alleles end up in the new population is completely up to chance
62
what are the processes that affect allele frequencies in a population?
- natural selection (stabilising and directional) -genetic bottleneck -genetic drift -founder effect
63
what is population genetics?
attempts to study the changes in allele frequencies within a population, over time - studies the variation in the alleles and genotypes within the gene pool and how their frequencies vary over time
64
what are the factors that can affect genetic diversity within a population?
population size mutation rate migration natural selection changes to the environment founder effect non-random mating genetic drift gene flow
65
what is meant by speciation?
when 2 populations of the same species become so genetically different that they can no longer interbreed and produce fertile offspring that become a different unique species
66
what is the hardy-weinberg equation? what is represented by p and q?
p2 + 2pq + q2 = 1 p+q= 1 p = probability of dominant allele A p2 = probability of AA q2 = probability of aa 2pq = probability of heterozygous Aa or aA q = probability of recessive allele a
67
what are the equations to find phenotypic probability for dominant allele and recessive allele?
dominant : p2+2pq recessive : q2
68
what is Hardy-Weinberg principle?
allele frequencies will remain constant from generation to generation
69
what are 5 conditions that must be met to ensure that allele frequencies will remain constant?
no mutation population isolation with no migration no natural selection very large population random mating
70
what is allopatric speciation?
formation of 2 different species from one original species due to geographical isolation (eg separated by each other due to lakes, rivers,oceans,mountains, which act as barriers) the isolated populations are now subject to different selection pressures and undergo independent changes to the allele frequencies , which may result in a mutation
71
what is sympatric speciation?
formation of 2 different species from one original species due to reproductive isolation (eg behavioural changes or mutations that impacted their courtship ritual or the time of the year when they are infertile) while the populations inhabit the same geographical location
72
what can lead to reproductive isolation?
biological and behavioural changes
73
what is reproductive isolation?
collection of mechanisms, behaviors, and physiological processes that prevent the members of two different species that cross or mate from producing offspring
74
what is artificial selection / selective breeding?
process by which humans choose organisms with desirable traits and selectively breed them together to enhance the expression of these desirable traits over time and over many generations
75
what is the process of artificial selection?
1 The population shows phenotypic variation 2 A breeder selects an individual with the desired phenotype 3 Another individual with the desired phenotype is selected. The two selected individuals should not be closely related to each other 4 two selected individuals are bred together 5 The offspring produced reach maturity and are then tested for the desirable trait. Those that display the desired phenotype to the greatest degree are selected for further breeding
76
what is inbreeding depression?
Decreased vigour in terms of growth, survival and growth, survival and fertility after generations of inbreeding. Increases the chance of harmful recessive alleles combining in an individual and being expressed in the phenotype Leads to decreased growth and survivability reduction of gene pool in a population
77
what is hybrid vigour?
Increased heterozygosity giving increased vigour of fertility, growth and survival; also called heterosis.
78
what are some ethical issue with artificial selection?
reduction in the gene pool Organisms inheriting harmful genetic defects (as there is a higher chance of harmful recessive alleles combining in an individual vulnerable to new diseases loss of their nervous disposition makes them easy preys some coat colours may make the animal difficult to camouflage
79
allopatric speciation
different selection pressures mutation occurs advantageous alleles are passed on change in allele frequency unable to interbreed

Biology (18 decks)

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