Meiosis And Variation Flashcards
Homologous chromosomes
The two chromosomes in a pair.
Same centromere position, same length, genes for same characteristics
Genes that are found on the same chromosome are called
Linked genes
How are homologous pairs made
One copy of the chromosome has come from the female parent and the other copy from male parent
Each gamete is
Haploid And has a single set of Chromosomes
A cell with full double set of homologous chromosomes is
Diploid
Meiosis produces
Genetically variable haploid cells which develop into gametes
Mitosis produces
Genetically identical diploid cells to make a multicellular organism
Meiosis
During Interphase, the homologous chromosomes duplicate so each is now made up of two _____
sister chromatids
At the start of meiosis 1 ___
Homologous chromosomes pair up so that they are aligned gene by gene
The homologous pairs when they are aligned link to form a
Bivalent
Genetic makeup is unique due to two processes during meiosis-
Crossing over
Independent assortment
Crossing over
During meiosis 1 homologous pairs of chromosomes swap part of genetic material
Independent assortment
Chromosomes from each pair are randomly allotted to the daughter cells irrespective of their maternal and paternal origin
Chiasma
Formed at crossing over position between homologous pairs
How many chiasma do human chromosomes usually have
Two or three
What do chiasmata do
Allow exchange of sections of dna between homologous chromosomes
Cytokinesis
Separates two cells
Mieosis 1 summary
- crossing over
- number of chromosomes halved, going diploid to haploid
- one cell splits to produce two genetically different cells
- each chromosome present in both cells has Teo sister chromatids which are no longer identical
Linked genes
Found on the same chromosome and therefore passed on together
Meiosis 2
Each of the two cells produces in meiosis 1 undergoes a further division during which the sister chromatids of each chromosome are separates
In mammals what gene controls the development of male caharcteristics
SRY sex determining region of Y chromosome
Heterogametic
Makes- XY
Homogametic
Females XX
Use linkage map to
find distance between linked genes and their frequency of recombination
Gamete mother cell
Gametocyte
X chromosome inactivation
Most of the X chromosome is permanently switched off
What advantage does x chromosome inactivation have
In female cells prevents a double dose of gene products which could be harmful to cells
How to find the number of different combinations of chromosomes
2 to power of haploid number
