Lecture--Chapter 6

Question 1

What are the characteristics of chloroplast DNA?

Answer 1

1. A single, circular chromosome of double stranded DNA, having 110-120 and about 150k base pairs.
2. Located in typically 10 or more nucleoids, with about 60 chromosomes per organelle.

Question 2

Inheritance by random sorting during cytokinesis:

Answer 2

chloroplast inheritance

Question 3

Inheritance where traits are transmitted through the cytoplasm of the egg:

Answer 3

maternal inheritance

Question 4

The mixture of more than one type of organellar genome within a cell or an individual:

Answer 4

heteroplasmy

Question 5

What are the characteristics of mitochondrial DNA?

Answer 5

1. A single, circular chromosome of double stranded DNA, but with a large size variance among different organisms.
2. Located in typically just a few nucleoids, with < 10 chromosomes per organelle.
3. Human mitochondrial genome has about 17k base pairs.

Question 6

transmission of mitochondria by sperm in species that generally have maternal inheritance

Answer 6

paternal leakage

Question 7

Mitochondria are constantly exposed to:

Answer 7

reactive oxygen species

Question 8

What are the 2 ways in which mitochondrial diseases occur?

Answer 8

1. Mitochondrial DNA mutations occur at high rates and their DNA repair mechanisms are extremely limited.
2. Human mitochondrial disease can be transmitted by a maternal inheritance pattern.

Question 9

a relationship in which one organism lives inside a host

Answer 9

endosymbiosis

Question 10

“life took over the earth not by combat, but by networking”

Answer 10

Lynn Margulis

Question 11

refers to a gene or chromosome modification that alters gene expression and phenotype, does not involve a change in the DNA sequence, and does not persist for many generations

Answer 11

epigenetics

Question 12

Characteristics of epigenetics:

Answer 12

1. Occurs early during production of gametes or during embryo development
2. Includes imprinting, gene silencing, position effect, reprogramming, carcinogenesis, maternal effects

Question 13

the process by which certain genes are expressed in a parent of origin specific manner

Answer 13

genomic imprinting

Question 14

Characteristics of genomic imprinting:

Answer 14

1. Imprinted alleles are silenced

2. Imprinting has been observed in insects, mammals, and flowering plants

Question 15

the process by which offspring express only one of the two parental alleles

Answer 15

monoallelic expression

Question 16

the mouse lgf2 gene encodes a growth hormone called:

Answer 16

insulin-like growth factor 2

Question 17

Characteristics of lgf2 gene:

Answer 17

1. Mutation of the allele, lgf2- produces a defective protein.
2. Functional lgf2 gene is necessary for normal size.
3. The mutation can lead to dwarfism–depending on the source of the allele.
4. Imprinting results in the expression of the paternal allele, but not the maternal allele.

Question 18

Paternal wt allele + maternal lgf2- —->:

Answer 18

normal offspring

Question 19

Paternal lgf2- allele + maternal wt allele —->:

Answer 19

dwarf offspring

Question 20

DNA methylation affects:

Answer 20

gene expression

Question 21

prevent transcription:

Answer 21

silencing

Question 22

imprinting control region:

Answer 22

segment of DNA that is methylated or not in paternal vs. maternal chromosome

Question 23

Characteristics of DNA methylation:

Answer 23

1. Usually, but not always, prevents transcription
2. Addition of one or more methyl groups to an imprinting control region
3. Can involve a single gene, even part or all of a chromosome

Question 24

Genomic imprinting process: Imprinting occurs during:

Answer 24

gametogenesis

Question 25

Genomic imprinting process: The imprint is maintained:

Answer 25

during embryogenesis and in adult somatic cells

Question 26

Genomic imprinting process: The imprint is ____ and _____ in germ cells.

Answer 26

erased; reestablished

Question 27

With imprinting:

Answer 27

either the female or male alleles can be the transcriptionally inactive form

Question 28

focuses on nutritional and environmental factors that influence epigenetic gene regulation

Answer 28

environmental epigenetics

Question 29

expresses a signaling protein that determines whether a mammal’s coat is banded or a solid colour:

Answer 29

Agouti gene — agouti (banded) or non-agouti (solid colour)

Question 30

Characteristics of the agouti gene:

Answer 30

1. In cats, the agouti dominant results in a tabby pattern

2. In mice, the agouti dominant results in yellow, fat individuals

Question 31

The Agouti Mouse Cross Experiment:

Answer 31

(A) control: agouti female x agouti male —> fat yellow babies
(B) experiment:
1. 1/2 of mated females fed normal mouse chow —> fat yellow mice
2. 1/2 of mated females given vitamin supplements —> thin brown mice
3. agouti gene expression was turned off

Question 32

Bisphenol-A Experiment:

Answer 32

(A) Mice fed BPA had increased fat, yellow babies, with decreased agouti gene methylation
(B) Dietary supplementation with folic acid gave normal brown mice and restored agouti gene methylation

Question 33

an inheritance pattern for phenotypes determined by the genotype of the mother

Answer 33

maternal effect

Question 34

____ observed that the water snail can have a right-handed coiled shell or a left-handed coiled shell

Answer 34

Arthur Boycott (1920s); crossing experiment gave a non-Mendelian pattern of inheritance

Question 35

____ crossed the heterozygous F1s, but observed an all dextral phenotype:

Answer 35

Alfred Sturtevant

Question 36

The ______ contains lots of gene products produced by maternal cells.

Answer 36

oocyte cytoplasm

Question 37

Gene products in the oocyte are based on:

Answer 37

the genotype of the mother, not the oocyte

Question 38

Products are transported from ____ to ____ of the oocyte and persist after fertilisation:

Answer 38

nurse cells; cytoplasm of the oocyte

Question 39

D gene products cause ___ that promotes a right-handed body plan:

Answer 39

egg cleavage

Question 40

Is there a maternal effect in humans?

Answer 40

Probably, but there is little firm evidence–many may result in embryos failing to develop; some studies have suggested maternal effect on height and systolic blood pressure.