Eukaryotic Genetics - Lecture 9

Question 1

What are the 3 domains of life?

Answer 1

○ Bacteria
○ Archaea
○ Eukarya

Question 2

How did eukaryotes come about?

Answer 2

○ Endosymbiotic interaction (fusion) between archaea and alpha protobacterium
○ Bacterium became modern mitochondria
○ Archaea stores genome in chromatin

Question 3

What features are unique to eukaryotes?

Answer 3

○ Multicellularity
○ Organs
○ Sexes

Question 4

What are telomeres?

Answer 4

○ Have a loop structure that stops them recombining with other DNA or fusing with other chromosomes
○ In most cells: telomeres shorten after each round of DNA replication and cell division (senescence)
○ In embryonic stem cells and germ cells: telomerase prevents shortening of chromosomes

Question 5

What are the two genomes that eukaryotes have?

Answer 5

○ Nuclear genome
○ Mitochondrial genome

Question 6

What is eukaryotic gene?

Answer 6

An inheritable sequence of DNA with an associated function contributing towards the phenotype of the organism during development and/or ageing

Question 7

What are the features of the nuclear genome?

Answer 7

○ DNA and histone proteins that form chromatin
○ Fundamental unit of chromatin is the nucleosome
○ Genes are organised into chromosomes
○ Inheritance is mitotic or meiotic

Question 8

What are the features of the mitochondrial genome?

Answer 8

○ DNA is coated in non-histone proteins
○ DNA is circular and smaller than nuclear genome
○ Mitochondria is maternally inherited
○ Inheritance is cytoplasmic and asexual

Question 9

What are the main genomic features?

Answer 9

○ Regulatory regions: recognised by factors controlling transcription
○ Coding: mRNA is translated to make a protein
○ Non-coding but transcribed: produce RNAs that are non-coding RNAs e.g. tRNA, rRNA
○ Intra-genic: DNA sequences within genes (introns)
○ Inter-genic: DNA sequences between genes

Question 10

What does mitosis do?

Answer 10

○ Ensures that both daughter cells inherit one copy of the duplicated genome
○ Cytoplasmic material can be asymmetrically distributed leading to reprogramming of one daughter cell

Question 11

What does meiosis do?

Answer 11

Produces haploid genomes to enable sexual reproduction and increase genetic diversity via recombination

Question 12

What is produced when a stem cell undergoes mitosis - symmetric division?

Answer 12

2 stems cells

Question 13

What is produced when a stem cell undergoes mitosis - asymmetric division?

Answer 13

1 stem cell and 1 differentiating cell

Question 14

What is the difference in meiosis between males and females?

Answer 14

○ Males: produce 4 sperm cells
○ Females: Produce an egg with a polar body

Question 15

What can happen in meiosis?

Answer 15

○ Independent assortment: generates different combinations of chromosomes in gametes
○ Crossing-over: recombination between non-sister chromatids in prophase I

Question 16

What are the stages in interphase?

Answer 16

○ G1: Cell growth
○ S: DNA replication
○ G2: Preperation for mitosis

Question 17

What happens in prophase in mitosis?

Answer 17

○ Chromosomes condense
○ Mitotic spindle is formed
○ Nuclear envelope breaks down
○ Chromosomes attach to mitotic spindle

Question 18

What happens in metaphase in mitosis?

Answer 18

○ Chromosomes line up at the equator of the cell
○ Sister chromatids attached to opposite poles of the mitotic spindle

Question 19

What happens in anaphase in mitosis?

Answer 19

○ Cohesion between sister chromatids is lost
○ Chromatids segregate to opposite poles driven by shortening microtubles

Question 20

What happens in telophase in mitosis?

Answer 20

○ Chromosome decondense
○ Nuclear envelope forms
○ Cytokinesis begins

Question 21

Meiosis I: What happens in prophase I?

Answer 21

○ Chromosomes condense
○Homologous chromosomes undergo pairing (synapsis)
○ Crossing over occurs

Question 22

Meiosis I: What happens in metaphase I?

Answer 22

Each pair of homologous chromosomes line up at the equator

Question 23

Meiosis I: What happens in anaphase I?

Answer 23

Homologous chromosomes separate to opposite poles (sister chromatids still attached to each other)

Question 24

Meiosis I: What happens in telophase I?

Answer 24

○ Each pole has one of the original pair of homologous chromosomes
○ Each chromosome still consists of two chromatids
○ Cytokinesis completes meiosis I

Question 25

Meiosis II: What happens in prophase II?

Answer 25

Chromosomes attach to spindle

Question 26

Meiosis II: What happens in metaphase II?

Answer 26

Individual chromosomes line up at the equator

Question 27

Meiosis II: What happens in anaphase II?

Answer 27

Sister chromatids separate to opposite poles

Question 28

Meiosis II: What happens in telophase II?

Answer 28

Each haploid daughter cells carries one chromosome of each type