Inheritance

Question 1

Mendelian law of inheritance that suggests if two plants differ in one trait the resulting hybrid will have the trait of one of its parents, rather than a mix or another trait entirely (e.g. a red flower crossed with a white flower will produce either a red or white flower)

Answer 1

Law of uniformity

Question 2

Mendelian law of inheritance that suggests that for any one trait, a parent will have a pair of alleles, and which allele is passed on is down to chance

Answer 2

Principle of segregation

Question 3

Mendelian law of inheritance that states that different pairs of alleles are passed down independently of each other e.g. a brown eyed, black haired person mating with a blue eyed, blond haired person can produce a blue eyed, black haired person

Answer 3

Principle of independent assortment

Question 4

Type of Mendelian inheritance where only one copy of a disease allele results in disease expression - the person has the disease if they are heterozygous

Answer 4

Autosomal dominant

Question 5

Chance of offspring inheriting an autosomal dominant disease with one affected parent

Answer 5

50%

Question 6

Chance of offspring inheriting an autosomal dominant disease if both parents are affected

Answer 6

75% (although in some cases homozygous offspring would die in utero, so would be 66% of live births)

Question 7

The probability of a genetic trait being expressed among the population who carry the particular genes

Answer 7

Penetrence

Question 8

Type of penetrance where anyone who has the genetic make up for a trait will express that trait

Answer 8

Complete penetrance

Question 9

Type of penetrance where someone can have the genetic make up for a trait but not express that trait

Answer 9

Incomplete penetrance

Question 10

Percentage penetrance of a trait

Answer 10

Percent of people who have the genetic make up for a trait who express that trait

Question 11

Difference in severity of a disease among people who have the genetic mutation causing that disease

Answer 11

Variable expression

Question 12

Phenomenon where an individual matches a particular genetic phenotype, but the traits are caused by environmental rather than genetic factors

Answer 12

Phenocopy

Question 13

Type of Mendelian inheritance where disorders are only seen when an individual is homozygous for the disease allele

Answer 13

Autosomal recessive

Question 14

Chance of offspring of two carrier parents inheriting an autosomal recessive condition

Answer 14

25%

Question 15

Change of offspring of two carrier parents becoming a carrier for an autosomal recessive condition

Answer 15

50%

Question 16

Change of offspring of two carrier parents being a non-carrier healthy individual

Answer 16

25%

Question 17

Chance of offspring of an affected individual and a non-carrier healthy individual inheriting an autosomal recessive condition

Answer 17

0%

Question 18

Chance of offspring of an affected individual and a non-carrier healthy individual becoming a carrier for an autosomal recessive condition

Answer 18

100%

Question 19

Chance of offspring of an affected parent and a carrier parent being a healthy non-carrier individual for an autosomal recessive condition

Answer 19

0%

Question 20

Chance of offspring of an affected parent and a carrier parent being affected by an autosomal recessive condition

Answer 20

50%

Question 21

Chance of offspring of an affected parent and a carrier parent being a carrier for an autosomal recessive condition

Answer 21

50%

Question 22

Chance of offspring of two affected parents being affected by an autosomal recessive condition

Answer 22

100%

Question 23

Process where females in early foetal development have one copy of their X chromosome in each cell silenced

Answer 23

X inactivation/lyonisation

Question 24

Structure made up by an inactivated X chromosome

Answer 24

Barr body

Question 25

Process of X inactivation

Answer 25

Methylation

Question 26

Parent copy of X chromosome which is inactivated

Answer 26

Random; some cells of a female embryo will have its male parent's X chromosome and other cells will have its female X chromosome inactivated and all cells resulting from those early cells will have the same X chromosome inactivated

Question 27

Type of inheritance where males only require the mutation on their single X chromosome, but females usually require mutations on both their X chromosomes which is very rare so largely males are affected

Answer 27

X-linked recessive

Question 28

Phenomenon where females can express an X-linked recessive condition with only a single disease allele if during X inactivation most of their normal alleles are inactivated leaving mostly disease alleles

Answer 28

Unfavourable lyonisation leading to manifesting heterozygotes

Question 29

Chance of a daughter of an affected male and a non-carrier healthy female being affected by an x-linked recessive condition

Answer 29

0% (unless in the case of unfavourable lyonisation)

Question 30

Chance of a daughter of an affected male and a non-carrier healthy female being a heterozygous carrier for an x-linked recessive condition

Answer 30

100%

Question 31

Chance of a son of an affected male and a non-carrier healthy female being affected by an x-linked recessive condition

Answer 31

0%

Question 32

Chance of a son of an affected male and a non-carrier healthy female being a healthy non-carrier for an x-linked recessive condition

Answer 32

100%

Question 33

Type of inheritance where both males and females only require one disease allele on an X chromosome to be affected

Answer 33

X-linked dominant

Question 34

Chance of a son of an affected mother and healthy father inheriting an X-linked dominant disease

Answer 34

50%

Question 35

Chance of a daughter of an affected mother and healthy father inheriting an X-linked dominant disease

Answer 35

50%

Question 36

Chance of a son of an affected father and healthy mother inheriting an X-linked dominant disease

Answer 36

0%

Question 37

Chance of a daughter of an affected father and healthy mother inheriting an X-linked dominant disease

Answer 37

100%

Question 38

Reasons for females to inherit X-linked dominant conditions more commonly than males

Answer 38

Equal risk of inheriting from an affected mother but only females can inherit from an affected father Some X-linked dominant conditions are fatal in embryo for males

Question 39

Parent mitochondrial DNA is inherited from

Answer 39

Mother

Question 40

Part of the sperm which does contain mitochondria

Answer 40

Body

Question 41

Purpose of mitochondria in the body of the sperm

Answer 41

Propels the tail | Shed when the sperm enters the ovum

Question 42

A phenomenon where the symptoms of a genetic disorder become apparent at an earlier age with each generation, seen in trinucleotide expansions

Answer 42

Anticipation

Question 43

Genetic disorders caused by an increased number of a certain codon (e.g. CGG)

Answer 43

Trinucleotide expansions

Question 44

Phenomenon where although structurally identical, certain genes are expressed differently depending on whether the gene has come from the mother or father

Answer 44

Genomic imprinting

Question 45

Phenomenon where a child receives two copies of a chromosome, or part of a chromosome, from one parent and no copies from the other parent

Answer 45

Uniparental disomy

Question 46

Potential issues caused by parental disomy

Answer 46

Can disrupt genomic imprinting, resulting in imprinting disorders Leads to homozygosity which can result in expression of autosomal recessive disorders

Question 47

Inheritance pattern where multiple genes as well as environmental factors influence whether a disease is present

Answer 47

Multifactorial inheritance

Question 48

Inheritance pattern where multiple genes but no environmental factors are present

Answer 48

Polygenetic inheritance

Question 49

Term for variations in genetic make up present in at least 1% of the total population, and associated with varied phenotype but not with disease

Answer 49

Polymorphism

Question 50

Polymorphism where restriction enzymes act at different site of DNA, resulting in different areas of DNA being cleaved

Answer 50

Restriction fragment length polymorphism

Question 51

Polymorphism where a single nucleotide is substituted at a certain point in the genome

Answer 51

Single nucleotide polymorphism

Question 52

Pattern within a genome where one or more nucleotides are repeated immediately adjacent

Answer 52

Tandem repeat

Question 53

Type of tandem repeat where up to ten nucleotides are repeated

Answer 53

Microsatellite

Question 54

Type of tandem repeat where more than ten nucleotides are repeated

Answer 54

Minisatellite

Question 55

Polymorphism where the number of tandem repeats in a specific area varies from person to person

Answer 55

Variable number of tandem repeats/copy number variations

Question 56

Effect in genetics where a population has a limited genetic variation due to being formed from a very small number of individuals out of a larger population

Answer 56

Founder effect

Question 57

Effect in genetics where the frequency of an allele is changed due to random chance

Answer 57

Genetic drift

Question 58

Effect where a beneficial mutation increases its frequency and becomes fixed in a population, which leads to a reduction in genetic variation of nucleotides which are near the beneficial mutation

Answer 58

Selective sweep

Question 59

Polymorphism of the serotonin transporter which may increase the risk of affective disorders and PTSD

Answer 59

Short allele of the 5HT transporter linked promoter region

Question 60

Situation where a single gene influences several characteristics

Answer 60

Pleiotropy

Question 61

Situation where a single gene influences several characteristics

Answer 61

Pleiotropy

Question 62

Presence in the same trait in a pair of twins

Answer 62

Concordance

Question 63

Trait that is not shared between twins i.e. presence of the trait in one twin and absence in the oher

Answer 63

Discordance

Question 64

Degree of variation in a phenotypic trait which is due to genetic variation between individuals; can be expressed as a percentage

Answer 64

Heritability

Question 65

Proportion of each genotype within a population e.g. AA, AB, BB

Answer 65

Genotype frequency

Question 66

Proportion of chromosomes within a population which contain a specific allele e.g. if a population contains the genotypes AA, AB, and BB it is the percentage of A alleles out of all the alleles

Answer 66

Gene frequency

Question 67

Law that states allele and genotype frequencies will remain constant in a population in the absence of other evolutionary influence

Answer 67

Hardy-Weinberg principle

Question 68

The phenomenon where genes which hinder survival and fertility are not passed on through generations

Answer 68

Natural selection

Question 69

The state of sharing a blood relationship which is genetically second cousins or closer

Answer 69

Consanguinity

Question 70

Interaction between different genes which are not alleles

Answer 70

Epistasis

Question 71

Phenomenon where the same disease phenotype can be caused by different mutations at different sites

Answer 71

Locus heterogeneity

Question 72

Phenomenon where the same phenotype can be caused by multiple different mutations at the same site

Answer 72

Allelic heterogeneity

Question 73

Inheritance pattern of familial frontotemporal dementia

Answer 73

Autosomal dominant

Question 74

Introduced the concept of endophenotypes

Answer 74

Gottesman and Shields

Question 75

Type of mutations seen in trinucleotide repeat disorders

Answer 75

Dynamic mutations

Question 76

Conditions associated with copy number variations

Answer 76

Autism Schizophrenia Idiopathic learning disability

Question 77

Assumptions made by the Hardy-Weinberg principle

Answer 77

``` No mutations occur No migration occurs Random mating occurs Population is large enough to compensate for genetic drift No natural selection occurs ```

Question 78

Inheritance pattern which shows vertical transmission

Answer 78

Autosomal dominant

Question 79

Inheritance pattern which shows horizontal transmission

Answer 79

Autosomal recessive

Question 80

Inheritance pattern which shows knight's move transmission

Answer 80

X-linked recessive

Question 81

Pattern where individuals with similar phenotypes mate together more often than would be expected by chance

Answer 81

Assortative mating

Question 82

Simple method to calculate the carrier frequency from the affected frequency for an autosomal recessive condition using the Hardy-Weinberg equation

Answer 82

Square root of the bottom number of the affected prevalence, then double the bottom number e.g. prevalence is 1/4900, square root is 1/70, carrier prevalence is 1/35

Question 83

Processes which explain most epigenetic variations found to date

Answer 83

DNA methylation | Histone modification