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Summary Introduction to genetics
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- University Of The Freestate (UFS)
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BIOLOGY: THE DYNAMIC SCIENCE 9781133592075CHAPTER 11
MEIOSIS
Sexual reproduction: I s the mixing of the nuclei of gametes to produce
an offspring
Meiosis: Meiosis is a specialised process of cell diving that occurs in animals to produce gametes
Sexual reproduction depends on meiosis.
What is a somatic cell?
A somatic cell is a body that has a diploid number of chromosomes
It has a full set of chromosomes (2n- chromosomes)
How many chromosomes does a gamete have?
A gamete has half the number of chromosomes of a somatic cell
It has a haploid number of chromosomes (n-number of chromosomes) due to the halfing effect of
meiosis
What occurs during Fertilization?
The nuclei of the sperm (spermatozoa) fuses with the nuclei of the egg (ova) to produce a specialized
cell called a Zygote where the chromosome number is restored
Evaluate the differences between asexual reproduction and sexual reproduction
Asexual reproduction: Produces genetically identical offspring (have the same genetic information
each other and the parent) due to mitotic cell division
Sexual reproduction: Produce genetically un-identical offspring ( different from each other and the
parent) due to meiotic cell division
What causes variability amongst offspring?
*Meiosis and *fertilization both mix genetic information into new combinations.
Mechanisms of Meiosis
Where does meiosis occur in humans and other animals?
Meiosis occurs in the gonads (primary reproductive organs) of animals
Where does meiosis occur in males and females? What is produce?
In female: Meiosis occurs in the gonads (ovary) to produce Ova (egg)
In Males; Meiosis occurs in the gonads (testes) to produce spermatozoa (sperm)
Define gametogenesis.
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, BIOLOGY: THE DYNAMIC SCIENCE 9781133592075
Is a cellular mechanism of gamete formation
Is the basis of gamete formation
The two representative of each chromosome in a somatic cell constitute a homologous pair
Traits of Homologous chromosomes
1. Homologous chromosomes have the same genes
2. Arranged in the same order in the DNA of the chromosome
3. One Chromosome is from the father (Paternal Chromosome ) and the other is from the mother
(Maternal chromosome)
What are versions of genes called?
Versions of genes are called Alleles
Are these versions of genes or alleles present in members of homologous chromosomes the same?
Alleles or Versions of genes of members of homologous chromosomes pairs may or may not be the
same.
Does everyone have a unique set of allele combination?
Yes, everyone has unique combination of alleles besides identical siblings
Why Meiosis 1 is called the reduction division? (2n > n)
Meiosis 1 separates the homologous pair, reducing the diploid chromosome number to a haploid
chromosome number
Why is Meiosis 2/ Mitosis called the equational division?
The number of chromosomes per cell remains unchanged
What maintains the number chromosomes in a somatic cell?
DNA replication
Mitosis
The meiotic cell cycle
How many stages are there in Meiosis?
Meiosis is separated into to two stages i.e. meiosis I and meiosis II in sexually reproducing animals
What occurs in pre-meiotic I interphase cell division?
In pre-meiotic cell division, DNA replicates and the chromosomal proteins replicate producing identical
chromatids of each chromosome
LZPDD
Meiosis 1
Prophase 1
Leptotene- Chromosomes condenses and come visible as single strands
Zygotene- Two chromosomes of each homologous pair undergo synapsis forming tetrads
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