Eukaryotic Genetics - Lecture 9 Flashcards
What are the 3 domains of life?
○ Bacteria
○ Archaea
○ Eukarya
How did eukaryotes come about?
○ Endosymbiotic interaction (fusion) between archaea and alpha protobacterium
○ Bacterium became modern mitochondria
○ Archaea stores genome in chromatin
What features are unique to eukaryotes?
○ Multicellularity
○ Organs
○ Sexes
What are telomeres?
○ 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
What are the two genomes that eukaryotes have?
○ Nuclear genome
○ Mitochondrial genome
What is eukaryotic gene?
An inheritable sequence of DNA with an associated function contributing towards the phenotype of the organism during development and/or ageing
What are the features of the nuclear genome?
○ DNA and histone proteins that form chromatin
○ Fundamental unit of chromatin is the nucleosome
○ Genes are organised into chromosomes
○ Inheritance is mitotic or meiotic
What are the features of the mitochondrial genome?
○ DNA is coated in non-histone proteins
○ DNA is circular and smaller than nuclear genome
○ Mitochondria is maternally inherited
○ Inheritance is cytoplasmic and asexual
What are the main genomic features?
○ 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
What does mitosis do?
○ 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
What does meiosis do?
Produces haploid genomes to enable sexual reproduction and increase genetic diversity via recombination
What is produced when a stem cell undergoes mitosis - symmetric division?
2 stems cells
What is produced when a stem cell undergoes mitosis - asymmetric division?
1 stem cell and 1 differentiating cell
What is the difference in meiosis between males and females?
○ Males: produce 4 sperm cells
○ Females: Produce an egg with a polar body
What can happen in meiosis?
○ Independent assortment: generates different combinations of chromosomes in gametes
○ Crossing-over: recombination between non-sister chromatids in prophase I
What are the stages in interphase?
○ G1: Cell growth
○ S: DNA replication
○ G2: Preperation for mitosis
What happens in prophase in mitosis?
○ Chromosomes condense
○ Mitotic spindle is formed
○ Nuclear envelope breaks down
○ Chromosomes attach to mitotic spindle
What happens in metaphase in mitosis?
○ Chromosomes line up at the equator of the cell
○ Sister chromatids attached to opposite poles of the mitotic spindle
What happens in anaphase in mitosis?
○ Cohesion between sister chromatids is lost
○ Chromatids segregate to opposite poles driven by shortening microtubles
What happens in telophase in mitosis?
○ Chromosome decondense
○ Nuclear envelope forms
○ Cytokinesis begins
Meiosis I: What happens in prophase I?
○ Chromosomes condense
○Homologous chromosomes undergo pairing (synapsis)
○ Crossing over occurs
Meiosis I: What happens in metaphase I?
Each pair of homologous chromosomes line up at the equator
Meiosis I: What happens in anaphase I?
Homologous chromosomes separate to opposite poles (sister chromatids still attached to each other)
Meiosis I: What happens in telophase I?
○ Each pole has one of the original pair of homologous chromosomes
○ Each chromosome still consists of two chromatids
○ Cytokinesis completes meiosis I
Meiosis II: What happens in prophase II?
Chromosomes attach to spindle
Meiosis II: What happens in metaphase II?
Individual chromosomes line up at the equator
Meiosis II: What happens in anaphase II?
Sister chromatids separate to opposite poles
Meiosis II: What happens in telophase II?
Each haploid daughter cells carries one chromosome of each type
