MCO Genetics Flashcards
Difference between genetics and genomics
- Genomics: Technology used to generate large data sets
- Genetics: Method of experimentation to understand cause and effect between genes
How long is human DNA in a cell
2 metres
3 parts to the chromosome stucture
- Telomeres
- Centromere
- Euchromatin
Karyotype definition
the number and visual Appearance of the chromosomes in the cell nuclei of an organism or species
What is a telomere
The end of the chromosome arm
What is a centromere
The region where the two sister chromatids are held together
What is a kinetochore
The protein complex on the chromosome where microtubules attached during cell division
What is euchromatin
Regions where you find lots of genes on the chromosome
What is heterochromatin
Regions found near the centromere, responsible for the structural movement of the chromosome. Doesn’t contain much DNA for expression.
What is a telocentric chromosome
Where the centromere is at the tip of the chromosome. There is only 1 arm.
What is acrocentric chromosome
Centromere is located near the end of the chromosome
What is a submetacentric chromosome
Where the centromere is quite not in the centre.
What is a metacentric chromosome
Where the centromere is in the centre of the chromosome.
What are the different length arms resulting from different centromere positions
- Short arms (p)
- Long arms (q)
Visual catalogue to provide notation on a chromosome
There are different bands produced by staining to provide notation
Genome sequencing
- Can locate a gene down to base pairs
- Each gene has a unique number
Mitosis
- Generate 2 identical daughter cells
- Diploid
- Used for multiplication, growth & tissue maintenance
Meiosis
- Four genetically distinct daughter cells
- Sexual reproduction, ‘shuffles the deck’
The cell cycle
- Interphase: G1, S, G2
- Cell division
What happens in interphase
Organelles and chromosomes replicate
Stages of mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
What happens in prophase
- Centrosome duplicates and begin to move to poles
- Chromosomes start condensing
- Nuclear membrane breaks down
- Spindle forms, extending from centrosomes and across cell
What happens in metaphase
- Centromere align on the metaphase plate.
- There is bipolar attachment
What happens in anaphase
Chromosomes migrate to opposite poles
What happens in telophase
- Chromosomes at poles
- Spindle disassembles
- Nuclear membrane reforms
What happens in cytokinesis
- Chromosomes decondense
- Cells divide
How are sister chromatids joined together
Joined together by cohesins which are broken down by separases
Meiosis stages
Meiosis 1 and meiosis 2
What happens in prophase 1
- DNA condenses
- Nuclear membrane breaks down
- Homologous chromosomes align & synaptonemal complex forms
- Chiasmata the exchange of segments in chromatids
- Spindle fibres form
- DNA fully condensed, synaptonemal complex breakdowns, & monopolar kinetochores attach chromosomes to spindle
What happens in metaphase 1
Kinetochores have aligned at the equator (metaphase plate)
What happens in anaphase 1
Monopolar attachment pulls homologous chromosomes to opposite poles
What happens in telophase 1
Diploid cell have formed
How has “shuffling the deck’ has occurred
- Independent assortment of parental chromosomes
- Crossing-over of chromosome arms
What happens in prophase 2, metaphase 2, and anaphase 2
Same but sister chromatids become chrosomes
Telophase 2
Four genetically distinct haploid cells
Differences in meiosis between male and females
Males: 4 gametes per meiosis
Females: 1 gamete meiosis
5 stages of prophase 1
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
What happens in leptotene
- Chromosomes start to condense & become visible
- Homolog pairing begins
- Double-strand DNA breaks are introduced (potential sites for crossing-over)
What happens in zygotene
- A synaptonemal complex begins to form between homologous pairs (Synapsis)
- Paired homologs now referred to as bivalents
What happens in pachytene
- Condensing of chromosomes continues
- Synaptonemal complex is complete
- Bivalents now have four sister chromatids (tetrads)
- Crossing-over is completed
What happens in diplotene
- Synaptonemal complex disassembles
- Each pair of sister chromatids begins to separate
- Chiasmata are visible regions of cross-over between non-sister chromatids
What happens in diakinesis
- Chromosomes repel each other
- Non-sister chromatids remain loosely associated via chiasmata
- Nuclear envelope disintegrates
- Monopolar attachment of chromosomes to spindle fibers
Function of synaptonemal complex
- Facilitates late stages of recombination
- Prevents homolg pairs from getting entangled
What is a univalent
An unpaired chromosome during prophase 1 of meiosis
Medel’s experimental method
- Assemble a robust experimental system
- Careful design and perform first experiment, and quantify results to generates lots of data
- Repeat same experiment with different starting material
- Analyse the collective data and derive predicted model
- Devise and execute experiments to test predictions
- Validate molecular basis of predicted gene(s)
First law of inheritance
Heredity is controlled by paired factors (alleles) that separate in gametes and are joined up in fertilisation
What did william bateson do
Applied mendelian genetics to animals
What did roland biffen do
Produced a wheat variety that contained resistance to yellow rust
What statistical test is used to validate genetics
Chi-squared
Different genetic models
- Drosophila: used for multicellular development
- Mice: for mammalian acquired immunity
- Pea plant: used by Mendel
Model for first law of inheritance
- Discrete trait
- Complete dominance
- Environmentally stable phenotype
What is the chromosome theory
Chromosomes are the unit of heredity
What is frequency of recombination
- The frequency that 2 genes are co-inherited. Depends on the physical distance between 2 genes.
- The smaller the frequency the closer they are physically
- The greater the frequency the further apart they are
- 0% tightly linked, or same gene
- 50% unlinked on different chromosomes or far apart
What is the linear model
Genes are ‘physically’ located in a linear manner along a chromosome
Units for recombination
1% recombination = 1 Map unit = 1 centiMorgan (cM)
What is positional cloning
To identify a gene based on the location on the chromosome