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52 Cards in this Set

  • Front
  • Back

What is inheritance?


The transmission of traits from one generation to the next

What is genetics?

The scientific study of heredity and hereditary variation

What are somatic cells?

Any cell in a multicellular organism except a sperm or egg cell or their precursor

What are germ cells?

A reproductive cell. Each mature germ cell is haploid

What is meant by haploid?

A cell which contains a single set of 23 chromosomes

Contains half the usual amount of DNA

What is meant by diploid?

A cell which contains two sets of 23 chromosomes

Contains the full set of DNA

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.

What is a homologous pair?

The two homologous chromosomes inherited. one from a father, one from a mother

What is a non-homologous chromosome?

A chromosome which does not have a matching: centromere position, length and/or staining partner as its pair

What are genes?

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses)

Where are genes located?

A locus on a chromosome

What are histone proteins?

Proteins that help with folding of DNA

DNA wrapped around histones then looped + coiled to prevent untangling

What does methylation do?

Affects how tightly coiled the DNA is + effectively switches genes off

What are the types of cell division?

Mitosis - normal cell lifecycle

Meiosis - for reproduction

What happens in prophase 1?

Chromosome duplication

HC pair up

Spindle formation

Nuclear envelope breaks down

chromosomes condense

What is crossing over?

Where the DNA molecules of sister chromatids are broken and are rejoined to each other

In what stage does crossing over occur?

Prophase I

Where does crossing over occur?

the chiasmata (x-shaped region)

Where do the spindle fibres radiate from?

The centrosome

What are spindle fibres?


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

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

What happens at anaphase I?

Homologs are separated

Chromosomes move to opposite poles, guided by spindle fibres

What allows the homologs to separate?

Breakdown of proteins that are responsible fro sister chromatid cohesion

What causes sister chromatids to move as a unit to the same pole?

Sister chromatid cohesion persists at the centromere

What happens at telophase I?

Each half of the cell now has a haploid set

Cytoplasm begins to split

Nuclear envelope reforms

What happens in cytokinesis I?

Cytoplasm splits

Two haploid daughter cells formed

What forms in telophase in animal cells?

Cleavage furrow

What happens in meiosis II?

Same as meiosis I but with chromosomes forming chromatids

What causes sister chromatids to not be identical come meiosis II?

Crossing over that occurs in meiosis I

What is formed in telophase + cytokinesis II?

Four genetically distinct haloid daughter cells

What is the structural relationship between chromosomes + chromatids?

A Chromosome is comprised of two chromatids

What is the relationship between DNA and chromatids?

Chromatids are vectors for genes - comprised of DNA

What are autosomes?

Pairs of chromosomes that are not sex determined

What is a centromere?

The part where chromatids join

What is the human karyotype?

an ordered display of the pairs of chromosomes in a cell

What does each pair of homologous chromosomes include?

One chromosome from each parent

When does mitosis occur?

Before cytokinesis, after G2 in the cell cycle

Where does mitosis occur?

In many tissues that need to replace cells

e.g. blood, epithelium of the small intestines

Why does mitosis occur?

to produce new cells that contain a diploid set

of chromosomes

Replace dead and removed cells

What is the difference between mitosis + meiosis?

Mitosis produces diploid daughter cells

Meiosis produces haploid daughter cells

Why is meiosis needed?

To allow offspring to be produced with half of their genetic info from each parent

What mechanisms contribute to genetic variation?


Reshuffling of alleles

independent assortment of chromosomes

Crossing over

Random fertilization

How do mutations contribute to genetic variation?

changes an organism's DNA

Creates different versions of genes called alleles

When does reshuffling of alleles occur?


What is independent assortment?

Where chromosomes have an equal chance of chromosomes from each parent lining up at metaphase I

What is random fertilisation?

Any egg fertilised by any sperm

What does crossing over produce?

recombinant chromosomes

What is epigenetics?

The study of chemical modification of specific genes or gene-associated proteins of an organism

How does mitosis conserve the number of chromosome sets?

By producing cells that are genetically identical to the parent cell

What happens as an organism grows + develops?

Chemical reactions activate + deactivate parts of the genome at strategic times + specific locations

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