Lecture 51. Non-Mendelian Inheritance

Question 1

What plant was used to discover transposable elements?

Answer 1

Maize

Question 2

What are transposable elements?

Answer 2

DNA sequences that can change their position within the genome

Question 3

When does ‘jumping’ occur

Answer 3

During mitosis

Question 4

What can affect ‘jumping’?

Answer 4

Environment (e.g temperature stress)

Question 5

What happens when a transposable element enters an exon?

Answer 5

Gene switches off

Question 6

What happens when a transposable element enters a promoter?

Answer 6

Gene switches on

Question 7

What are transposable elements also known as?

Answer 7

‘Jumping’ genes

Question 8

Do ‘jumping’ genes just occur in plants?

Answer 8

No, they also occur in animals

Question 9

What is epigenetics the study of?

Answer 9

Heritable changes in gene expression that are not caused by heritable changes in DNA sequence

Question 10

What is methylation?

Answer 10

Methyl group can tag DNA and activate or repress genes

Question 11

What happens when DNA is coiled around a histone?

Answer 11

DNA is inacessible for transcription so gene is inactive

Question 12

What organelles did Ruth Sager find contain DNA?

Answer 12

Mitochondria and chloroplasts (mtDNA & cpDNA)

Question 13

What is the biochemical evidence of symbiosis in mitochondria?

Answer 13

Mitochondria communicate with the nucleus via trafficking of proteins and RNAs

Question 14

What is the genetic evidence of symbiosis in mitochondria?

Answer 14

The nucleus contains genes that encode mitochondrial proteins

Question 15

What is the mitochondrial genome?

Answer 15

Circular genome
Contains genes for tRNAs, rRNAs, cytochrome oxidase, ATPase subunit & NADH-dehydrogenase

Question 16

What is the size of the mitochondrial genome in humans?

Answer 16

~16kb

Question 17

What is the size of the mitochondrial genome in yeast?

Answer 17

~80kb

Question 18

What is the size of the mitochondrial genome in plants?

Answer 18

~100kb to 2 Mb

Question 19

What is the chloroplast genome?

Answer 19

Circular genome
Contains genes for redox proteins involved in electron transport for photosynthesis
Also contain a lot of non-coding DNA

Question 20

What is the size of the chloroplast genome?

Answer 20

~80-600kb

Question 21

Why do the mitochondria and chloroplasts have the exact same phenotype and genotype as the mother?

Answer 21

Meiotic segregation does not take place in organelles because they are acquired at cell division from the maternal cytoplasm

Question 22

What are the two types of petite yeast mutants?

Answer 22

Segregational and vegetative

Question 23

What are segregational mutants?

Answer 23

Mendelian segregation following meiosis
Genes are located in the nucleus

Question 24

What are vegetative mutants?

Answer 24

Non-Mendelian pattern of inheritance
Genes are located in the mitochondria

Question 25

What ratio does the tetrad of progeny show after crossing a wild type with a segregational petite?

Answer 25

2:2

Question 26

What ratio does the tetrad of progeny show after crossing a wild type with a neutral petite?

Answer 26

4:0

Question 27

What ratio does the tetrad of progeny show after crossing a wild type with a suppressive petite?

Answer 27

0:4

Question 28

What do neutral petites lack?

Answer 28

Most of their mitochondrial DNA

Question 29

What do suppressive petites lack?

Answer 29

Small segments of mtDNA

Question 30

What parent do yeast offspring inherit mitochondria?

Answer 30

Both parents

Question 31

What is MERRF?

Answer 31

Myoclonic epilepsy & ragged-red fiber disease

Question 32

What nucleotide substitution causes MERRF?

Answer 32

Lysine in tRNA

Question 33

What are the symptoms of MERRF?

Answer 33

Spasms and abnormal tissues, accumulation of lactic acid in the blood, and uncoordinated movement

Question 34

What are the uses of mitochondrial genome sequencing?

Answer 34

Maternity analysis Phylogenetic systematics Population genetics

Question 35

Why do mitochondrial genome sequencing?

Answer 35

Easy to isolate and PCR amplify mtDNA due to high copy number per cell Maternal inheritance mtDNA enables analysis of maternal population structure without confusion of male-mediated gene flow No recombination of mtDNA so very slow to evolve Mutations that do occur are rapidly fixed in a population

Question 36

What can phylogenetic analysis using mtDNA trace?

Answer 36

Roots of humanity

Question 37

What is maternal inheritance?

Answer 37

Maternal phenotypes that are caused by variation in genes located in the nuclear genome

Question 38

What are examples of maternal inheritance?

Answer 38

Maternal factors (proteins or mRNA) that are deposited in the oocyte prior to fertilisation Shell coiling in snails

Question 39

What is genomic imprinting?

Answer 39

A form of gene expression in which an allele of the affected gene is marked or ‘imprinted’ in one of the parents, and can be passed on through meiosis to the offspring

Question 40

How is the epigenetic mechanism marked?

Answer 40

By methylation or histone modification