Intro To Euk Genetics Flashcards
What are genes?
Carriers of heritable information
Genes play a crucial role in determining the phenotype of an organism.
What defines a eukaryote?
Rise of complex life
Organisms with complex cells containing a nucleus
Eukaryotes include animals, plants, and fungi.
How are genes inherited?
Through processes such as mitosis and meiosis
Mitosis involves somatic cells, while meiosis is involved in gamete formation.
What is the rise of complex life associated with?
Coupling energy with information
This is a significant evolutionary development in the history of life.
What is a eukaryote gene?
An inheritable sequence of DNA with an associated function contributing towards the phenotype (function) of the organism during development and/or aging
How many genomes do eukaryotes have?
Two: mitochondrial and nuclear
The mitochondrial genome is maternally inherited.
What is the fundamental unit of chromatin?
Nucleosome
Chromatin is made up of DNA and histone proteins.
What is the main genomic feature that controls transcription?
Regulatory regions
These regions are recognized by factors controlling gene expression.
What is the difference between mitosis and meiosis?
Mitosis ensures that both daughter cells inherit one copy of the duplicated genome.
However, the cytoplasmic material can be asymmetrically distributed leading to reprogramming of one daughter cell
Meiosis produces haploid genomes to enable sexual reproduction and increase genetic diversity via recombination
What is the role of telomeres?
Stabilize the ends of chromosomes
Act like caps to keep linear structure
Telomeres prevent chromosomes from recombining or fusing with others.
What happens to telomeres during DNA replication?
They shorten after each round of replication until it becomes a stop signal for replication
This shortening is prevented in certain cell types by the enzyme telomerase.
What is the significance of crossing-over in meiosis?
Generates new combinations of alleles on chromosomes
This increases genetic variability among offspring.
What is independent assortment in meiosis?
The generation of different combinations of chromosomes in gametes
It can generate 2^n different gametes, where n is the haploid chromosome number.
True or False: Mitosis and meiosis both occur in the G2 phase of the cell cycle.
True
Both processes begin after DNA replication in the G2 phase.
How many crossovers occur in humans during meiosis?
40-95 per meiosis
This number is generally higher in females than in males.
What does the term ‘haploid’ refer to?
A cell that has one complete set of chromosomes
Haploid cells are produced during meiosis.
Fill in the blank: The period between successive mitoses is called _______.
interphase
Interphase includes G1, S, and G2 phases.
What type of cell division produces gametes?
Meiosis
This process leads to the formation of haploid cells for sexual reproduction.
What is the cell cycle?
The period between the birth of a cell and its division into daughter cells
What phases does mitosis and meiosis start from?
G2 phase with replicated chromosomes
List the stages of mitosis.
- Prophase
- Metaphase
- Anaphase
- Telophase
List the stages of meiosis I.
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I
What is crossing over?
Exchange of genetic material between non-sister chromatids in each bivalent
What is the ploidy of the cell after telophase I of meiosis?
Haploid
Fill in the blank: Mitosis and meiosis start from the _____ phase.
G2
Here, chromosomes have been replicated and sister chromatids have formed
True or False: In mitosis, homologous chromosomes separate.
False
True or False: Cytokinesis occurs at the end of both mitosis and meiosis.
True
What is a genome?
Sum of the genes of a specific species
What is the nuclear genome?
- DNA and histone proteins that form chromatin
- Fundamental unit of chromatin is the nucleosome (produces the chromatin)
- Genes organised into chromosomes
- Inheritance is nuclear (mitotic or meiotic = sex)
What is the mitochondrial genome?
- DNA is coated with non-histone proteins
- DNA is circular and much smaller than nuclear genome
- Mitochondria are maternally inherited
- Inheritance is therefore cytoplasmic and asexual (through fission like bacteria)
What are the main genomic features?
- Regulatory regions - recognised by factors controlling transcription
- Coding - the mRNA is translated to make a protein
- Non-coding but transcribed - produce RNAs such as tRNA, rRNA or other non-coding RNAs
- Intra-genic - DNA sequences within genes e.g. introns (splicing occurs)
- Inter-genic - DNA sequences between genes (‘junk’ DNA but now thought to have function)
What is a karyotype?
Condensed chromosomes at metaphase during mitosis
Where does mitosis occur?
In somatic cells (any cell not involved in reproduction)
Where does meiosis occur?
In sex cells (egg & sperm)
What are the stages of mitosis?
Early Prophase
- chromosomes condense to become visible
- mitotic spindle is formed (composed of microtubules which are formed from centromeres)
Late Prophase
- nuclear envelope breaks down
- chromosomes attach to mitotic spindle
Metaphase
- chromosomes line up at the equator of the cell
- sister chromatids attach to opposite poles of the mitotic spindle
Anaphase
- cohesion between sister chromatids is lost
- chromatids segregate to opposite poles driven by shortening of microtubules
Telophase
- chromosomes decondense so are no longer visible
- nuclear envelope reforms and forms 2 nuclei
- cytokinesis begins
What are the stages in meiosis I ?
Known as reductional cell division as it goes from diploid to haploid
Prophase I
- chromosomes condense
- homologous chromosomes undergo synapsis (pairing)
- crossing over occurs forming bivalents each containing 4 chromatids
Metaphase I
- each pair of homologous chromosomes line up at the equator
Anaphase I
- homologous chromosomes separate to opposite poles
- sister chromatids are still attached to each other
- failure to separate here results in nondisjunction
Telophase I
- each pole has one of the original pair of homologous chromosomes
- cell is now haploid
- each chromosome still consists of 2 chromatids
- cytokinesis completes meiosis I
What are the stages in meiosis II ?
Similar to mitosis
Prophase II
- chromosomes attach to spindle
Metaphase II
- individual chromosomes line up at the equator
Anaphase II
- sister chromatids separate to opposite poles
Telophase II
- each haploid daughter cell carries 1 chromosome of each type
