Biology Review Guide

Review Questions & Answers

(1/23)

1. Explain the difference between haploid and diploid cells. Tell where in an organism they are found. Tell how they are produced. A haploid cell is a cell that contains one complete set of chromosomes. Gametes(sperm and ova) are haploid cells that are produced by meiosis. Diploid cells contain two complete sets (2n) of chromosomes. Diploid cells reproduce by mitosis making daughter cells that are exact replicas. Some examples are skin, blood, muscle cells (also known as somatic cells).

2. In 2-4 sentences compare and contrast mitosis and meiosis including the steps, purpose and products. Mitosis and meiosis are types of nuclear division that make different types of cells. Mitosis makes diploid cells that are genetically identical. It takes place throughout an organism’s lifetime and is involved in asexual reproduction. During meiosis, diploid cells undergo 2 cell divisions that result in 4 haploid cells. Meiosis occurs in sex cells, produces gametes, increases genetic diversity and produces genetically unique cells. It takes place only at certain times in an organism’s life cycle and is involved in sexual reproduction.

(1/24)

3. What is gene linkage? Under what circumstances are genes linked? What makes it more likely that two genes will be linked in any given process of meiosis? Genetic linkage is the tendency for genes located close together on the same chromosome to be inherited together. Factors that are likely to cause a gene to be linked is how close together the genes are on the same chromosome.

(2/3)

4. Mendel proposed the law of segregation. Explain why the law by telling what is segregated and when it occurs. The law of segregation is Mendel’s 1st law stating that (1) organisms inherit 2 copies of genes, one from each parent, and (2) organisms donate only one copy of each gene in their gametes because the gametes seperate during gamete formation.

5. Mendel’s Law of Independent assortment works with many genes, but not all. What is actually assorting independently? What test did Mendel do that caused him to propose the law of independent assortment? When a trait does not assort independently we say it is ______? The law states that allele pairs seperate from one another during gamete formation. Unlinked genes (genes located on different chromosomes) assort independently because chromosome pairs assort independently during meiosis. Mendel tested his theory through experiments concerning pea plants. independently into the newly formed gametes. A di-hybrid cross is what Mendel performed to propose the law of independent assortment. When a trait does not assort independently we say it is a sex-linked gene. Some genes sort together when they are located on the same chromosome.

(2/4)

6. Write a brief definition and give an example of each of these patterns of inheritance: true dominance, incomplete dominance, co-dominance, multiple allele inheritance, polygenic traits .

True dominance: When one of the alleles is dominant meaning that the gene could be

homozygous or heterozygous in order for the dominant trait to be present. However

you must have a homozygous set in order for the recessive trait to be shown. Such as

the height of a pea plant

Incomplete dominance: When the alleles are heterozygous the trait will be a mixture

of both of the traits. Such as if two flowers are pollinated to create a flower and one

of them is white and the other is red then the new flower would be pink.

Co-dominance: When the alleles are heterozygous the two traits will be equally

distributed. Such as if two chickens mate and one has white feathers and the other

has black feathers then the offspring of the two could have a combination of both

white and black feathers.

Multiple allele inheritance: When more than two alleles are inherited from one gene.

Such as human blood type.

Polygenic traits: When one trait is controlled by multiple genes. Such as the height of

humans because different genes control the length of different bones which each are

a part of the person's height.

7. What are sex-linked traits? Why are males more likely to get them? When is a gene on a chromosome equally likely to be expressed in males and females? Sex-linked traits are traits that are determined by an allele located on the sex chromosome. Males are more likely to get them because they are found on the x chromosome and if it is recessive it will only take one for a male to inherit the trait while it will take two for a female. It is equally likely to be expressed in males and females when it is dominant because that means it will only take one to inherit the trait.

8. What is a karyotype? What does it match up? A karyotype is an image of all the chromosomes in a cell. It matches up chromosome

pairs 1-23.

(2/7)

9. In your own words, tell what does gel electrophoresis does? Fill in the blanks to help describe gel electrophoresis: It uses ____________to separate DNA fragments by _______ . Gel electrophoresis is a way to separate and analyze macromolecules. It uses

electricity to separate DNA fragments by size.

(2/10)

10. What does PCR (Polymerase Chain Reaction) produce? Why is it important? PCR (Polymerase Chain Reaction) produces multiple copies of a section DNA. This is

important because it allows scientists to work with DNAs and DNA samples that they

previously could not. In addition, it allows for multiple tries /copies if needed.

11. What is genetic engineering? What characteristic of living things enables us to accomplish it? Genetic engineering is the process of altering a cell’s genetic material to perform a specific function. It is possible because plants, which is what genetic engineering has been tested using, get genetic information from a “dad” and “mom”.

(2/11)

12. What is a knockout organism and what does it help us understand? A knockout organism is a genetic technique where one of an organism’s genes is made

unable for use. It helps us understand the roles of a specific gene or DNA region. Scientists remove one gene to conclude what its function is.

13. What is recombinant DNA? Recombinant DNA contains genes from more than one organism.

Other Questions

14. Explain the data that led Mendel to propose the theory of dominance.The data that led Mendel to propose the theory of dominance was that when he crossed tall and short plants they all were tall however once he crossed this generation 75% of them were tall and 25% were short. This led him to say that some genes are recessive while others are dominant. In this case, tall was dominant and short was recessive.

15. How many alleles can be produced from TtGg organism? What are they? Four alleles can be produced from the TtGg organism. These alleles are TG, Tg, tG, and tg.