ineritence patterns

Question 1

dominant def

Answer 1

an allele always expressed in the phenotype regardless of copy number

Question 2

recessive def

Answer 2

an allele that is only expressed if present on both chromosome homologs

Question 3

homozygous def

Answer 3

Homozygous – both homologs have the same allele at a given locus

Question 4

heterozygous def

Answer 4

Heterozygous – the allele at a given locus differs between homologs

Question 5

co dominant def

Answer 5

Co-dominant – two alleles that are both expressed in the heterozygote

Question 6

Mendelian Inheritance

Answer 6

every individual has two copies (allele) of each gene
and each allele segregates into a copy of inheritance material in a gamete
alleles reunite randomly at fertilisation

Question 7

trait

Answer 7

Trait – a genetically determined characteristic; similar to a phenotype

Question 8

carrier

Answer 8

a heterozygote with one recessive allele at a given locus; usually refers to a disease allele

Question 9

mono hybrid cross

Answer 9

mating between two individuals that differ in only one trait

Question 10

dihybrid cross

Answer 10

mating between two individuals that differ in two traits

Question 11

linkage

Answer 11

occurs between two genes that are located near each other on a chromosome

Question 12

why does independent assortment occur?

Answer 12

because if crossing over and recombination

Question 13

why is crossing over and recombination done

Answer 13

• separate alleles into different gametes
• Alleles previously linked to the same chromosome are inherited independently

Question 14

how does chromosomes become recombinant

Answer 14

Homologous chromosomes pair during meiosis (prophase I) and form chiasmata
Breakages at chiasmata allow sections of DNA to be swapped between homologs
Chromosomes become recombinant

Question 15

mendelian inheritance - dominance

Answer 15

observed all meme era of the f1 gen had the same phenotype
- indentical to one of the pure bred parents

When he crossed individuals from F1, the other pure-bred phenotype reappeared with a frequency of 25% in F2 gen

can also be effected by the environment

THE RATIO OCCURS EVERYTIME PARENTS MATE NOT DEPENDANT ON NUMBER OF OFFSPRING

Question 16

what did the reappearance of missing phenotype prove - mendelian’s dominance

Answer 16

Blending of parental units of heredity
Each individual has two copies of a gene

Question 17

what did mendel conclude

Answer 17

that one trait is dominant over the other and hybrids are therefore ‘unstable’

Question 18

pedigree

Answer 18

chart that shows inheritance of a trait / disorder through family generations

Question 19

what’s a proband - pedigree

Answer 19

first person in a tree to be diagnosed with the condition

Question 20

what’s a proband - pedigree

Answer 20

first person in a tree to be diagnosed with the condition

Question 21

autosomal dominant

Answer 21

if an effected parent mates with an unaffected parent, there is a 50% chance that the disease will be inherited

Question 22

characteristics of autosomal dominant inheritance

Answer 22

Question 23

polydactyly

Answer 23

autosomal dominant disorder
has extra digit (s)
caused by dominant allele

Question 24

autosomal recessive diseases

Answer 24

rare - but more common than dominant
must be inherited from both parents

heterozygous carriers - but will not express it phenotypically

generation skip can occur

consanguinity is common in family trees

Question 25

cystic fibrosis

Answer 25

autosomal recessive disorder must be inherited from both parents causes severe damage to the lungs, digestive system and other organs in the body

Question 26

reduced penetrance

Answer 26

when individuals with disease genotype do not always express disease phenotype norm happens in disorders with autosomal dominant inheritance pattern

Question 27

retinoblastoma

Answer 27

malignant eye tumour autosomal dom disease obligate carries have affected parent and child

Question 28

what’s a penetrance rate

Answer 28

% of obligate carriers that express disease

Question 29

de novo mutation

Answer 29

proband causes de novo likely cause of disease if parents and grandparents are unaffected recurrence risk for siblings is not elevated Recurrence risk for offspring is elevated Most autosomal dominant diseases arise from de novo mutation 7/8 achondroplasia sufferers Expression of disease phenotype reduces likelihood of reproduction

Question 30

de novo germline mosaicism

Answer 30

Germline mosaicism may account for multiple siblings in a family without a history of a disease Mutation occurs in parental germline Few if any somatic cells are affected Recurrence risk to siblings is the same as if the parent were affected Occurs in 20% of haemophilia A cases

Question 31

de novo germline mosaicism

Answer 31

Germline mosaicism may account for multiple siblings in a family without a history of a disease Mutation occurs in parental germline Few if any somatic cells are affected Recurrence risk to siblings is the same as if the parent were affected Occurs in 20% of haemophilia A cases

Question 32

structure of mitochondria

Answer 32

Mitochondria have a double membrane which controls transfer of metabolites: Outer membrane is smooth Inner membrane is highly folded into cristae which are covered in stalked particles Presence of two membranes creates two internal compartments: Intermembrane space plays an important role in the proton pump Matrix contains *DNA, ribosomes and enzymes

Question 33

mitochondria- cytoplasmic inheritance

Answer 33

Mitochondrial inheritance is extranuclear and maternal Mitochondria divide by binary fission* Average human sperm contains 50-75 mitochondria Average human egg contains 100,000 – 600,000 mitochondria In the zygote, male mitochondria are diluted by the female mtDNA is used extensively in evolutionary biology and ancestry studies

Question 34

what’s the function of mitochondria

Answer 34

site of atp synthesis

Question 35

why do mitochondria have their own genome

Answer 35

many proteins needed in the etc

Question 36

what are nucleoids

Answer 36

highly condensed and circular structures that store mtDNA

Question 37

how many genes do mtDNA have

Answer 37

37genes 13 involved in oxidative phosphorylation 22 are tRNA genes 2 are rRNA genes for each ribosome subunit**

Question 38

maternal inheritance - mitochondria

Answer 38

males can inherit but not transmit females can transmit to both genders

Question 39

mitochondrial inheritance disease

Answer 39

mtDNA has a very high mutation rate 10x higher than nDNA Oxidative phosphorylation creates free radicals that act as mutagens Most mtDNA mutations are lethal because of ATP demands during embryogenesis If viable carriers of the mutation are likely to suffer from neurodegeneration Neurones consume 20% of all ATP no cure can chase deafness blindness diabetes heart/liver failure