Meiosis Flashcards
What are advantages of asexual reproduction?
It’s rapid so organisms can take advantage of resources in the environment, can occur is sexual reproduction fails and all offspring have genetic material to survive is current environment
What are disadvantages of asexual reproduction?
No genetic variety so weaknesses are inherited an if environment change, all are susceptible
What are the stages in meiosis 1?
Prophase I, Metaphase I, Anaphase I and telophase I
What happens during prophase I?
Chromatids condense (46 chromosomes in humans x2 = 92 chromatids), homologous chromosomes pair up and crossing ver occurs at points called chias where DNA is exchanged
What happened during metaphase I?
Bivalents randomly line up at metaphase plate
What happens during anaphase I?
Pairs of chromosomes move apart and independently segregate
What happens during telophase I?
Two cells are formed with 46 chromatids, each with different combinations of genetic information from mother and father
What are the stages in meiosis II?
Prophase II, metaphase II, anaphase II and telophase II
What happens during prophase II?
Each daughter cell contains 46 chromatids and chromosomes recondense
What happens during metaphase II?
Pairs of chromatids line up along the equator at 90 degrees to previous division
What happens in telophase II?
Four daughter cells formed each with 23 chromosomes
What are haploid chromosomes?
They have the same genes
How many chromosomes are in diploid cells?
46
How many chromosomes are in haploid cells?
23
What are bivalents?
Pairs of homologous chromosomes
What is a gene?
A section of DNA that codes for a polypeptid
What is a locus?
It is something every gene has which is its physical position on a chromosome
What are alleles?
The different forms of every gene
What are the two kinds of chromosomes within an organism?
Long and short
What are the versions of chromosomes in a diploid cell?
There are 2 versions, one from the mother and one from the father
What’s the result of genetic variation?
Some organisms will be better adapted to survive
What are the sources of genetic variation?
Crossing over, independant assortment of chromosomes at metaphase I, independant assortment of chromosomes at metaphase II, random fertilisation and gene mutation
What is the result of crossing over?
It shuffles alleles
How is independant assortment of chromosomes at metaphase I a source of genetic variation?
The pole to which chromosomes is pulled to is random and independent of any other chromosomes
How is independant assortment of chromosomes at metaphase II a source of genetic variation?
After crossing over has occurred, the two chromatids of a chromosome are genetically different and alignment is random and independant
How is random fertilisation genetic variation?
It takes place when 2 gametes fuse to form a zygote and each gamete has a unique combination of genes and any of the numerous male gametes can fertilise the egg
How is gene mutation genetic variation?
DNA is very stable but bases can change during DNA replication and mutations in gametes will be present in all cells of the offspring
What happens at anaphase II?
Individual chromosomes are pulled apart
