Chapter 8 Meiosis and Crossing Over Part 2 8.12-8.24

8.12 Chromosomes and homologous chromosomes

How many chromosomes do people have in a somatic cell?

How are homologous chromosomes similar? How are they different?

What is the exception to the general pattern of human chromosomes?

How many pairs of chromosomes in humans are sex chromosomes?

How many pairs of chromosomes in humans are autosomes?

8.13 Gametes have a single set of chromosomes

Explain the haploid and diploid portions of the human life cycle using the following

Words; haploid, diploid, gametes, fertilization, and zygote.

8.14 Meiosis reduces chromosome number from diploid to haploid

How many cell divisions are there in meiosis? What are they called?

How many stages of Interphase are there in meiosis?

8.15 Comparing mitosis and meiosis

What is a tetrad?

Make a Venn diagram showing the similarities and differences in mitosis and meiosis?

8.16 Causes of variation in meiosis

This is the most useful diagram to memorize concerning meiosis. It is highly abbreviated, which is good, and it shows independent assortments.

·  Important points in this section:

·  Mutation is a very common form of genetic variation.

·  Changes in an organism’s DNA can lead to the expression of new genes.

·  Genetic variation is a driving force for natural selection.

·  Meiosis produces variation from the random alignment of homologous chromosomes in metaphase 1.

·  Humans can produce 223 chromosome combinations, or about 8 million.

·  Random choice in mates leads to genetic variation.

If a species has a diploid number of 24. How many chromosomal combinations are possible in the expressed gametes?

8.17 Homologous chromosomes - same genes, different forms of a gene scenario

Compare the genetic information found on the tetrad below.

8.18 The fourth source of genetic variation in meiosis

Explain the process illustrated below

8.19 Karyotype

Describe in detail the karyotype below.

8.20 Chromosome abnormality – Down’s syndrome

Down syndrome is caused by trisomy 21 and the incidence of this syndrome is related to the age of the mother.

8.21 Non disjunction

How can non disjunction produce abnormal chromosome in gametes?

8.22 Abnormal sex chromosome numbers

Fill in the table below:

Sex chromosome / Syndrome
XXY
XYY
XXX
XO

8.23 Polyploidism

What type of organisms produce a tetraploid zygote, and why is that significant?