Download General Biology Chapter 5 Homework Meiosis This is the homework

General Biology
Chapter 5 Homework
Meiosis
This is the homework for all of Chapter 5. This is due on Tuesday, January
24 at the beginning of class. If it is late the grade will be 50% off. Please answer
completely on a separate sheet of paper.
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1. What is the function (purpose) of meiosis? The function of Meiosis is to divide a
diploid reproductive cell and make four haploid gametes for sexual reproduction.
2. How many times does the cell divide in meiosis? There are 2 cell divisions in
Meiosis.
3. What is the ploidy (sets of chromosomes) of cells before and after meiosis? In
humans the reproductive cell at the beginning is diploid with 46 chromosomes (23
pairs). So at the beginning it is 2n and the end result is 4 haploid cells (n).
4. The cells that are produced in meiosis are called sex cells or gametes.
5. What is crossing over and when does it occur? Crossing over is when the
homologous chromosomes pair up in tetrads in Metaphase of Meiosis and swap some
genetic information to create genetic variability in the population.
6. What is a tetrad? When two homologous chromosomes pair up in Metaphase I of
Meiosis in the process of synapsis. This formation is called a tetrad.
7. Compare Mitosis and Meiosis. Make a chart. This looks like a good essay
question for the test. (hint)
Mitosis
Meiosis
Somatic cells
Asexual reproduction
1 cell division
Metaphase chromosomes line up
Anaphase – chromotids pulled apart
Result – 2 diploid cells
sex cells
sexual reproduction
2 cell divisions
Metaphase tetrads line up
Anaphase – homologous chromsome apart
Result – 4 haploid cells
8. Define the following: gametes, zygotes, spermatogenesis, oogenesis, and polar
body.
Gametes – the 4 haploid cells that are the result of Meiosis.
Zygote – 2 gametes unite to form this and this is the first cell of a new individual.
Spermatogenesis – the process of the forming of sperm
Oogenesis – the process of forming the ovum or egg.
Polar body – The three unused cells in the process of oogenesis.
Basic Genetics:
9. List Mendel’s three concepts and briefly define each one.
The concept of unit characteristics states that an organisms characteristics are caused by
factors or genes.
The Concept of Dominance and Recessive states that a trait that expresses itself when
genes are opposing traits are present is dominant. The trait that is hidden is called the
recessive trait.
The concept of segregation is the genes separate so that there is only one gene for each
characteristic in each gamete. Meiosis
10. Define the following: phenotype, allele, genotype, homozygous, and heterozygous.
Phenotype – the physical characteristic
Allele – an alternate form of a gene.
Genotype – the specific gene that an organism has on its chromosomes
Homozygous – both alleles are the same ex. TT
Heterozygous – the alleles are different ex. Tt
11. What is a test cross and why would someone use it?
A test cross is used when you have an organism that has a dominant phenotype, but you
are unsure of the genotype is homozygous or heterozygous. So you can mate that
organism with an organism that is recessive and homozygous. If you have any offspring
in the F1 generation that shows the recessive trait, then the unknown was heterozygous.
12. Two organisms heterozygous for a single trait are crossed. What is the expected
genotypic ratio of the offspring? Explain.
Set up a Punnett Square using any letters you want. Both parents are heterozygous so the
offspring genotypes are going to be 50% heterozygous, 25% homozygous dominant, and
25% homozygous recessive.
13. What is incomplete dominance and codominance. What is the difference?
Incomplete dominance is when you have two alleles for a gene, but one is not completely
masking the other one. For example a red flower mates with a white and the offspring is
pink.
Codominance is when both alleles are equally expressed. So you can see both in the
offspring.
14. What are multiple alleles?
This is when there are many possible alleles in the population. For example, blood type
in humans can be A, B or O.
15. What does Mendel’s concept of Independent assortment state?
The separation of one set of genes or alleles is not affected by the separation and thus are
independent of the separation of another set of alleles. One gene is not related to another
during the separation in Meiosis.
16. What is multiple gene interaction and pleiotropy and how are they different.
This is polygenic, where 2 or more genes work together to get one trait. For example,
eyes in humans is many genes for eye color.
17. What are the sex chromosomes and the autosomes? How are they different?
Sex chromosomes are the chromosomes that determine the sex of an individual. Sex
chromosomes are notated as X and Y. The autosomal chromosomes are the other nonsex chromosomes in the cell.
18. What are sex-linked traits?
Sex – linked traits are traits that are on the X chromosome. Like color-blindness and
hemophilia
19. Why are sex-linked traits passed from father to daughter but not father to son? Can a
mother give a sex-linked trait to her daughter?
The father only passes the Y chromosome to his son, and sex linked traits are only on the
X chromosome. So, no the father can not pass sex-linked traits to his son. Yes the
mother will pass an X to her daughter and the father will pass the X chromosome as well
to his daughter.