UNIT 3.2 Flashcards
Prokaryotic Genetics
Features:
Evolve:
Bacteria:
*Check Good Notes for Diagrams
Prokaryotes have circular and naked DNA (plasmid)
Prokaryotes do not possess a nucleus - genetic material is found in the cytoplasm in a region called the nucleoid
*Bacterial cells can exchange plasmids via their sex pili
*Bacterial conjugation → This horizontal gene transfer allows bacteria to evolve new features within a generation
*Bacteria are used for lab manipulation (eg: insulin production) since it can self-replicate and autonomously synthesize proteins
Eukaryote Genetics
Linear DNA associated with histone
Eukaryotic cells have 2 sets of chromosomes called homologous chromosomes
Eukaryote Genetics: Homologous chromosomes
Chromosomes feature:
Chromosomes in humans
Homologous chromosomes: a pair of chromosomes (one from each parent) that are the same length and contain the same genes in the same location
- May carry different alleles
*An organism’s traits are largely determined by its sets of chromosomes, but the environment also plays a role in the traits the organism will develop
CHROMOSOMES IN HUMANS:
- The first 22 chromosomes in humans are known as autosomes
- The 23rd pair of chromosomes: sex chromosomes/heterosomes
Human somatic cells
*46 chromosomes consisting of
*2 sets of
*22 homologous chromosomes + a pair of non-homologous sex chromosomes
Females have 2 X chromosomes
Males have XY chromosomes
X chromosome is larger than Y chromosome
Organisms with different numbers of chromosomes are unlikely to interbreed successfully
Identifying Genes (3)
1) Chromosomes may differ:
Length
2) Position of the centromere
3) The location of the gene in the chromosome (locus)
Homologous Pairs
*Check Good Notes for Diagrams
Homologous chromosomes must be separated in gametes (via meiosis) prior to reproduction
Diploid & Haploid
Diploid
1) Two sets of homologous chromosomes (2n)
2) Somatic/body cells
3) Produced by mitosis
4) Pair of homologous chromosomes
5) In humans, 23 pairs 46 chromosomes
Haploid: Produced from diploid cells
1) One set of chromosomes (n)
2) Gametes/Sex cells
3) Produced by meiosis
4) One chromosome of each pair
5) In humans n=23 pairs
Total 46 chromosomes
Haploid
Features:
Autosome Pairs:
Sex Chromosomes
*Check Good Notes for Diagrams
*The father gamete controls the sex offspring
After haploid sperm and haploid egg fuse to form a zygote, the embryo that develops through mitotic division will have 46 chromosomes in each of its cells
All of the autosome pairs are homologous because both the maternal copy and the paternal copy contain the same genes in the same positions on the chromosome
Although the sex chromosomes have different genes and different lengths, they do share a homologous region that allows them to act as a pair during meiosis
Karyograms
To Determine Sex
To identify Down Syndrome
*Check Good Notes for Diagrams
A diagram or photograph of the chromosomes present in a nucleus arranged in homologous pairs of descending length
The chromosomes are visible in cells when undergoing mitosis, most clearly in metaphase
Karyogram to determine sex:
Chromosome 23: XY → men
Chromosome 22: XX → women
Karyogram to identify Down syndrome:
3 chromosomes will be found on chromosome 21
Karyotypes
Determine via a process that involves:
The number and types of chromosomes in a cell
Determine via a process that involves:
*Harvesting cells (usually from a fetus or white blood cells of adults)
*Chemically inducing cell division, then arresting mitosis while the chromosomes are condensed
*The stage during which mitosis is halted will determine whether chromosomes appear with sister chromatids or not
Karyotyping
Performed pre-naturally to identify the sex of offspring or diagnose potential chromosome abnormalities
Autoradiography
Created by who:
Used:
*Check Good Notes for Diagrams
Autoradiography was created by John Cairns to measure the length of DNA molecules
Cairns used autoradiography to visualize the chromosomes whilst uncoiled, allowing for more accurate indications of length
By using tritiated uracil (3H-U), regions of active transcription can be identified within the uncoiled chromosome
