6.2 Patterns of Inheritance Flashcards
1
Q
what is a Gene?
Genetic Variation
A
the basic unit of heredity
2
Q
what is a Genotype?
Genetic Variation
A
the full set of genes in an organism
3
Q
what is a Phenotype?
Genetic Variation
A
the observable characteristics of an organism
4
Q
what is a Locus?
Genetic Variation
A
the position of a particular gene on a chromosome
5
Q
what is an Allele?
Genetic Variation
A
alternative form of the same gene.
6
Q
what are the genetic causes of variation?
Genetic Variation
A
A. gene mutations
B. chromosome mutations during meiosis
C. gamete formation during meiosis
7
Q
what are the causes of phenotypic variation?
Genetic Variation
A
genetics and the environment
8
Q
what are the environmental causes of variation?
Genetic Variation
A
D. the environment
E. the impact of environment on genes
9
Q
A
What are the three types of mutagenic agents?
Genetic Variation
A
- physical
- chemical
- biological
10
Q
what are examples of physical mutagenic agents?
Genetic Variation
A
- UV
- gamma
- x rays
11
Q
what are examples of chemical mutagenic agents?
Genetic Variation
A
- free radicals
- mustard gas
- nitrous acid
12
Q
what are the examples of biological mutagenic agents?
Genetic Variation
A
- viruses
- food contaminants e.g mycotoxins from fungi
- transposons (jumping genes)
13
Q
what effects can genetic mutations have?
Genetic Variation
A
harmful, advantageous or neutral. these are either persistant or random
14
Q
B
when do chromosome mutations occur?
Genetic Variation
A
meiosis
15
Q
what type of chromosome mutations can occur?
Genetic Variation
A
- deletion
- inversion
- translocation
- duplication
- non disjunction
16
Q
what is deletion?
Genetic Variation
A
when part of a chromosome containing genes and regulatory sequences is lost
17
Q
what is inversion?
Genetic Variation
A
when part of a chromosome break off, turn 180° and reattach. some may not be fully expressed/
18
Q
what is translocation?
Genetic Variation
A
when a piece of chromosome breaks off and becomes attached to another. the gened transferred aren’t transcribed
19
Q
what is duplication?
Genetic Variation
A
when a piece of chromosome leads to too much expression of a protein, disrupting metabolism
20
Q
what is non disjunction?
Genetic Variation
A
when a pair of chromatids fail to separate leaving one gamete with an extra chromosome.
21
Q
what is aneuploidy?
Genetic Variation
A
when the chromosome number in kargotype is not an exact multiple of haploid number.
22
Q
what is polyploidy?
Genetic Variation
A
when a diploid gamete is fertilised.
23
Q
how is a triploid zygote made?
Genetic Variation
A
when a diploid gamete is fertilised by a haploid gamete
24
Q
how is a tetraploid zygote made?
Genetic Variation
A
when two diploid gametes are fused.
25
# C
how does sexual reproduction create variation?
| Genetic Variation
- random fertilisation
- independent assortment
- crossing over
26
# D
what are examples of environmental factors that create variation?
| Genetic Variation
accents, lanaguge, scars, losing a limb
27
# E
what is an example of the environment acting on genes?
| Genetic Variation
plants kept in dim light after germination or without sufficent magnesium.
28
how do these deficiencies act on genes?
| Genetic Variation
- plant has genotype to make chlorophyll
- chlorophyll production limited
- plant cannot photosynthesise due to environment
29
what is meant by monogenic cross inheritance?
| Monohybrid Inheritance
inheritance of a characteristic that is controlled by a single gene but may have 2+ alleles.
30
who was Gregor Mendel?
| Monohybrid Inheritance
an austrain monk who established the basics of inheritance, including dominant and recessive alleles via peas.
31
why did Mendel use pea plants?
| Monohybrid Inheritance
- easy to grow
- natuarlly self fertilising
- easy to cross fertilise artifically
- have 7 distinct observable characteristsics e.g colour, stem length, wrinkles etc.
32
what are true breeding strains?
| Monohybrid Inheritance
strains of plant (pea in this case) where traits were unchanged for generations.
33
why did Mendel use true breeding strains?
| Monohybrid Inheritance
to avoid the appearance of unexpected traits in offspring.
34
what is a monohybrid cross?
| Monohybrid Inheritance
mating individuals from contrasting true breeding parents strains to determine dominant and recessive alleles.
35
how did Mendel perfom a monohybrid cross?
| Monohybrid Inheritance
## Footnote
PUNNETT SQUARES USED
- mated individuals from contrasting true breeding parents -> P1
- the offspring from this cross (F1) were phenotypically identical to parent with dominant allele (100% Tt)
- F1 were allowed to self fertilsie to make F2
- the F2 generation will give 25% chance of recesssive allele. (25% TT, 25% tt, 50% Tt)
36
what is test crossing used for?
| Monohybrid Inheritance
to determine whether an organism showing the dominant characteristic is homozygous dominant or heterozygous
37
how does test crossing work?
| Monohybrid Inheritance
## Footnote
PUNNETT SQUARES USED
crossing the organism with the dominant characteristic with another that is **homozygous recessive**
38
what does it mean if any offspring show the recessive trait in test crossing?
| Monohybrid Inheritance
the parent (investigated organism) must have been heterozygous.
39
what is Dihybrid Inheritance?
| Dihybrid Inheritance
the inheritance of 2 genes from 2 seperate loci on different chromosomes
40
what did Mendel deduce from his dihybrid crosses?
| Dihybrid Inheritance
- alleles of 2 genes are inherited independently.
- each gamete will have one allele for each locus.
- independent assortment means any one allele can combine with any other allele.
41
what is the ratio of dihybrid inheritance?
| Dihybrid Inheritance
9:3:3:1
42
is the chance of one trait being inherited influenced by the other?
| Dihybrid Inheritance
no.
43
what did Mendel study?
| Dihybrid Inheritance
the inheritance of seed shape and seed colour in pea plants
44
how did Mendel investigate this?
| Dihybrid Inheritance
crossed true bred yellow and round pea plants (YYRR) with true bred green and wrinkled pea plants (yyrr)
45
what traits did the F1 generation have?
| Dihybrid Inheritance
yellow and round, so heterzygous.
46
what equation is used to predict traits in dihybrid crosses?
| Dihybrid Inheritance
product of individual probabilities = combined probability of occurence.
47
how can we predict F2's traits?
| Dihybrid Inheritance
## Footnote
PUNNETT SQUARE USED!
consider the 2 crosses as two independent monohybrid crosses and then use equation
48
# EXAMPLE
what is the probability of F2 generation being yellow and round?
| Dihybrid Inheritance
- 3/4 will be yellow, 1/4 will be green
- 3/4 will be round, 1/4 will be wrinkled
- 3/4 x 3/4 = 9/16
49
what is meant by multiple alleles?
| Multiple Alleles
when a characteristic has 3 or more alleles in the population's gene pool
50
what is codominance?
| Multiple Alleles
when both alleles present in the genotype of a heterozygous individual contribute to the phenotype.
51
what are human blood groups an example of?
| Multiple Alleles
multiple alleles and codominance
52
what is blood group determine by?
| Multiple Alleles
3 alleles of a single gene on chromosome 9
53
what does the human blood group gene code for?
| Multiple Alleles
isoagglutinogen on surface of erythrocytes.
54
# **
what are the genotypes and phenotypes of human blood groups?
| Multiple Alleles
IAIA or IAIO = A
IBIB or IBIO = B
IAIB = AB
IOIO = O
55
which blood group alleles are dominant?
| Multiple Alleles
IA and IB
56
how many alleles will an individual have for blood group?
| Multiple Alleles
only 2 out of the 3 available
57
what are the 4 coat colours of rabbits?
| Multiple Alleles
1. Agouti (Wild)
2. Albino
3. Chinchilla
4. Himalayan
58
what is an agouti coat?
| Multiple Alleles
- grey base, yellow band and a black tip
- dominant over all alleles (C)
59
what is an albino coat?
| Multiple Alleles
- no pigment at all
- recessive to all alleles (c)
60
what is a chincillia coat?
| Multiple Alleles
- a silvery grey, missing a yellow band
- dominant (Cch) over himalayan
61
what is a himalayan coat?
| Multiple Alleles
- white with black feet.
- recessive to only chinchilla (Ch)
62
what is an example of codominance in animals
| Codominance
- coat colour in short horn cattle has 2 alleles CW for White and CR for Red
- cattle that are homozygous have their respective colours
- cattle that are heterozygous have a roan coat.
63
what is the inheritance in short horn cattle?
| Codominance
- if red and white cattle are bred, all offspring will have **ROAN COATS**
- if roan cattle are bred, all offspring will have all 3 phenotypes (50% roan, 25% white, 25% red)
64
what are examples of codominance in humans?
| Codominance
- MN blood groups
- ABO blood groups
- sickle cell anaemia
65
why are MN blood groups an example of codominance?
| Codominance
- controlled by a gene with 2 alleles
- gene codes for protein of erythrocyte surface
- children of a heterozygous couple will have **GROUP MN**
66
why are ABO blood groups an example of codominance?
| Codominance
someone with IAIB genotype will express both and have both type of isoagglutinogen.
67
why is sickle cell anaemia an example of codominance?
| Codominance
in heterozgous people, half haemoglobin is normal (HBn) and half is abnormal (HBs)
68
what is an example of codominance in plants?
| Codominance
some types of camellia flower have red petals, some have white.
if these are crossed, the offspring will have both red and white petals as both alleles expressed.
69
what is sex linkage?
| Sex Linkage
when a particular gene is located on a sex chromosome
70
what is a homogametic sex chromosome?
| Sex Linkage
the XX chromsome in females
71
what is a heterogametic sex chromosome?
| Sex Linkage
the XY chromosome in males.
72
how is sex in mammals determined?
| Sex Linkage
two chromosomes/heterosomes: X and Y
73
which is larger, X or Y?
| Sex Linkage
X - contains over 2000 genes whilst Y contains less than 100
74
why is X linkage more common?
- x chromosome is larger
- part of the X chromosome doesn't have an homologous region on the Y so only one allele present and is therefore always expressed.
75
what does it mean if the female has a faulty allele on one X?
| Sex Linkage
she will have a functioning copy on the other X
76
what happens if a male inherits the faulty allele on the X?
| Sex Linkage
it will result in a genetic disease
77
how are male chromosomes described for X linked genes?
| Sex Linkage
as functionally haploid or hemizygous; they cannot be hetero or homozygous
78
what are examples of X linked diseases?
| Sex Linkage
- haemophillia
- duchenne muscular dystrophy
- colour blindness
79
why are Y linked diseases rare?
| Sex Linkage
as there is little room on the Y chromosome for anything other than genes controlling testes formation and function
80
what is Haemophillia A?
| Sex Linkage
blood being unable to clot fast enough, leading to bleeding and internal haemorrhage
81
what causes Haemophillia A?
| Sex Linkage
lack of the coagulation factor 8 which is coded for on a mutated allele on the non homologous region in females.
82
what are the alleles for haemophillia?
| Sex Linkage
## Footnote
PUNNETT SQUARE USED!
XHXh - female carrier
XhY - male sufferer
83
what causes sons to inherit haemophillia?
| Sex Linkage
if Xh is passed down.
84
what is X-Inactiviation?
| Sex Linkage
when one X chromosome is inactivated at random (either male or female) to ensure the effective dosage of X-linked genes is equalized between men and women.
85
what is an example of sex linkage in cats?
| Sex Linkage
the allele CO produces ginger fur whilst CB produces black.
cats with XCO and XCB have patches of both colours in their fur.
86
what happens during X-Inactivation in cats?
| Sex Linkage
the orange allele (CO) is only expressed in cells where black allele is inactivated and vice versa.
87
what is an autosome?
| Autosomal Linkage
a chromosome that doesn't determine sex
88
what is an autosomal linkage?
| Autosomal Linkage
when gene loci present on the same autosome are quite likely to be inherited together
89
hwo many autosomal linkage groups are there in humans?
| Autosomal Linkage
22 as 22 autosome pairs.
90
what genes are inehrited together in autosomal linkage?
| Autosomal Linkage
ones that are closely located on the same chromosome
91
why does autosomal linkage reduce variation?
| Autosomal Linkage
as there are fewer gene combinations of alleles
92
what causes offspring to be of parental type?
| Autosomal Linkage
crossings where linkage is a contributing factor.
93
what causes more genetic variation?
| Autosomal Linkage
genes on seperate chromosomes
94
what happens if linked genes **aren't** affected by crossing over?
| Autosomal Linkage
## Footnote
DIAGRAMS IN NOTES!
they are inheirted as one unit.
95
is there variation when no crossing over occurs?
| Autosomal Linkage
no.
96
what is recombination?
| Autosomal Linkage
the reassortment of genes or traits into different combinations from those of their parents
97
what is a recombinant?
| Autosomal Linkage
offspring with a genotype unlike either parent.
98
what happens if linked alleles **are** affected by crossing over?
| Autosomal Linkage
## Footnote
DIAGRAMS IN NOTES!
they are not inherited as one unit.
99
what is the ratio of inheritance when linked alleles are crossed over?
| Autosomal Linkage
12:1:1:2
100
what does this ratio depend on?
| Autosomal Linkage
length as the further apart 2 gene loci, the more likely recombinant genes are to form.
