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52 Cards in this Set
- Front
- Back
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What is inheritance? |
Heredity The transmission of traits from one generation to the next |
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What is genetics? |
The scientific study of heredity and hereditary variation |
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What are somatic cells? |
Any cell in a multicellular organism except a sperm or egg cell or their precursor |
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What are germ cells? |
A reproductive cell. Each mature germ cell is haploid
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What is meant by haploid? |
A cell which contains a single set of 23 chromosomes Contains half the usual amount of DNA |
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What is meant by diploid? |
A cell which contains two sets of 23 chromosomes Contains the full set of DNA |
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What is a homologous chromosome? |
A pair of chromosomes of the same length, centromere position and staining pattern that possess genes for the same characteristics at corresponding loci. |
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What is a homologous pair? |
The two homologous chromosomes inherited. one from a father, one from a mother |
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What is a non-homologous chromosome? |
A chromosome which does not have a matching: centromere position, length and/or staining partner as its pair |
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What are genes? |
A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses) |
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Where are genes located? |
A locus on a chromosome |
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What are histone proteins? |
Proteins that help with folding of DNA DNA wrapped around histones then looped + coiled to prevent untangling |
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What does methylation do? |
Affects how tightly coiled the DNA is + effectively switches genes off |
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What are the types of cell division? |
Mitosis - normal cell lifecycle Meiosis - for reproduction |
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What happens in prophase 1? |
Chromosome duplication HC pair up Spindle formation Nuclear envelope breaks down chromosomes condense |
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What is crossing over? |
Where the DNA molecules of sister chromatids are broken and are rejoined to each other |
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In what stage does crossing over occur? |
Prophase I |
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Where does crossing over occur? |
the chiasmata (x-shaped region) |
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Where do the spindle fibres radiate from? |
The centrosome |
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What are spindle fibres? |
microtubules |
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What happens in metaphase I? |
Chromosomes align at metaphase plate (centre) with one chromatid facing each pole Both chromatids of each homolog are attached to kinetochore microtubules from one pole
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How do the chromosomes align at the metaphase plate? |
Microtubules from one pole will attach to the two kinetochores, one at the centromere of homolog |
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What happens at anaphase I? |
Homologs are separated Chromosomes move to opposite poles, guided by spindle fibres |
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What allows the homologs to separate? |
Breakdown of proteins that are responsible fro sister chromatid cohesion |
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What causes sister chromatids to move as a unit to the same pole? |
Sister chromatid cohesion persists at the centromere |
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What happens at telophase I? |
Each half of the cell now has a haploid set Cytoplasm begins to split Nuclear envelope reforms |
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What happens in cytokinesis I? |
Cytoplasm splits Two haploid daughter cells formed |
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What forms in telophase in animal cells? |
Cleavage furrow |
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What happens in meiosis II? |
Same as meiosis I but with chromosomes forming chromatids |
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What causes sister chromatids to not be identical come meiosis II? |
Crossing over that occurs in meiosis I |
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What is formed in telophase + cytokinesis II? |
Four genetically distinct haloid daughter cells |
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What is the structural relationship between chromosomes + chromatids? |
A Chromosome is comprised of two chromatids |
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What is the relationship between DNA and chromatids? |
Chromatids are vectors for genes - comprised of DNA |
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What are autosomes? |
Pairs of chromosomes that are not sex determined |
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What is a centromere? |
The part where chromatids join |
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What is the human karyotype? |
an ordered display of the pairs of chromosomes in a cell |
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What does each pair of homologous chromosomes include? |
One chromosome from each parent |
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When does mitosis occur? |
Before cytokinesis, after G2 in the cell cycle |
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Where does mitosis occur? |
In many tissues that need to replace cells e.g. blood, epithelium of the small intestines |
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Why does mitosis occur? |
to produce new cells that contain a diploid set of chromosomes Replace dead and removed cells |
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What is the difference between mitosis + meiosis? |
Mitosis produces diploid daughter cells Meiosis produces haploid daughter cells |
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Why is meiosis needed? |
To allow offspring to be produced with half of their genetic info from each parent |
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What mechanisms contribute to genetic variation? |
Mutations Reshuffling of alleles independent assortment of chromosomes Crossing over Random fertilization |
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How do mutations contribute to genetic variation? |
changes an organism's DNA Creates different versions of genes called alleles |
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When does reshuffling of alleles occur? |
Meiosis |
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What is independent assortment? |
Where chromosomes have an equal chance of chromosomes from each parent lining up at metaphase I |
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What is random fertilisation? |
Any egg fertilised by any sperm |
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What does crossing over produce? |
recombinant chromosomes |
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What is epigenetics? |
The study of chemical modification of specific genes or gene-associated proteins of an organism |
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How does mitosis conserve the number of chromosome sets? |
By producing cells that are genetically identical to the parent cell |
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What happens as an organism grows + develops? |
Chemical reactions activate + deactivate parts of the genome at strategic times + specific locations |
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What are epigenetic tags? |
Include methylation that influences the level of transcription that can occur of particular genes As cells grow + divide, epigenetic tags are faithfully reproduced |
