BIOLOGY

Worksheet: Unit 3 Review

1.Define the following terms:

• Homozygous-• heterozygous -• true breeding- • genotype- • phenotype-• non-disjunction- • co-dominance- • incomplete dominance- • linked genes- • genetic engineering- • cloning-

Homozygous- two of the same allele (i.e. EE or ee)

Heterozygous- Two different alleles (i.e. Ee or Ss)

True-breeding- Means the same thing as pure-bred. Will always produce the same offspring.

Genotype- The “letter” combination. Describes the two alleles an organism has (i.e. EE, Ee, ee)

Phenotype- The physical characteristic that results from a gene (i.e. Tall or short, Red or white)

Non-disjunction- When chromosomes do not separate during meiosis. Results in gametes with extra or too few chromosomes

Example: would result in Down Syndrome, Klinefelters Syndrome, Turner’s Syndrome)

Co-dominance- Both alleles are dominant and both expressed in offspring.

(i.e. Red and White hair are dominant in cattle. A purebred red is crossed with a purebred white cow and results in a cow that is roan in color- has both red and white hair)

Incomplete dominance- Neither allele is dominant.

red flower crossed with white flower and produces pink flowers in offspring

Linked genes- Genes that are located on the same chromsome. Usually inherited together- they’re “linked”

Genetic engineering- changing of an organisms DNA to give new trait

Cloning- creating a genetically identical copy of gene or of an organism

2.What do you call the process where two gametes fuse?

Fertilization

3. What is the name of the cell that is formed as a result of this fusion?

Zygote

4.What is crossing-over (what process does it occur in, and what is the result of this process)?

When chromosomes cross over each other during meiosis and exchange bits and pieces of themselves

5.Describe the process of DNA replication. (where does it occur and what is the result)

DNA making copy of DNA. Occurs in nucleus of cell. Requires certain enzymes to catalyze reaction.

6.Complete the chart below comparing DNA and RNA:

DNA RNA

Type of sugar Deoxyribose Ribose

Nitrogen base A,T,C,G A,U,C,G

Complimentary bases

A-T C-G A-U C-G

Double or Single stranded?

Double Single

7.Blood type is determined by multiple alleles. Complete the chart below showing possible genotypes and phenotypes of blood type (page 205)

Phenotype Genotype Type A IAIA, IAi

Type B IBIB, IBi

Type AB IAIB

Type O ii

8.A human karotype shows 22 pairs of autosomes, and one pair of sex chromosomes.

9. A male has the genotype XY and a female has the genotype XX

10.In the process of transcription a DNA sequence reads CATTGA, what would the complementary mRNA strand that would read?

CATTGA

GUAACU

11. The genes on DNA contain instructions to assemble proteins

12.The monomers of proteins are amino acids

13. Three nitrogen bases make up a codon for an amino acid.

14.State Mendel’s principles of genetics.

a. What is the Principle of Dominance?

Some alleles are dominant and some are recessive

b.What is the Law of Independence Assortment?

allele pairs separate independently of each other during meiosis

15.Be able to use the genetic code chart. What are the amino acids coded for with the following codons?

a.UUU-

b.UUC-

c. ACG-

d.CCU-

e.AUU-

f. AAA-

g.GUC-

h.GCC-

15.Be able to use the genetic code chart. What are the amino acids coded for with the following codons?

a.UUU- Phe

b.UUC- Phe

c. ACG- Thr

d.CCU- Pro

e.AUU- Ile

f. AAA- Lys

g.GUC- Val

h.GCC- Ala

16.Summarize the process of translation; (where does it occur and what is the result. Include the three types of RNA involved)

RNA making Proteins. Occurs in the cytoplasm on the ribosomes. Involves all three types of RNA (mRNA, tRNA, and rRNA)

17. What did Mendel call the “factors” that determine traits?

Genes

18.What organisms do Mendel’s principles apply to?

All living things

19.What causes mutations in DNA?

a. Are all genetic mutations expressed? Explain

No. May not affect phenotype. May not change protein produced. May occur in non-coding part of DNA

b.What created oil-eating bacteria?

Induced mutations (radiation)

20.What is the purpose of Punnett squares?

A tool to predict the possible offspring of a genetic cross

21.State the phenotypic ratio of a heterozygous dihybrid cross?

9:3:3:1

22. Why would a scientist or breeder use selective breeding?

To try and combine certain traits in offspring to produce desired results

23. What is inbreeding and how does it occur?

Inbreeding is when two closely related organisms are crossed. Increases the chances that recessive alleles will combine in offspring

24. Skin color in humans is a result of Polygenic inheritance.

25. What are the possible gametes produced by the parent genotypes below?

a.RrYy- RY, Ry, rY, ry

b. rrYY- rY only

c. SSDD- SD only

26. Colorblindness is a sex-linked trait. Why do males exhibit colorblindness more than females?

Because the genes are carried on the X chromosome and males only have one X chromosome. If they have the recessive allele they will have the disorder

27. Complete the following table comparing Mitosis to Meiosis:

MITOSIS MEIOSISNumber of cells produced

2 4

Haploid or diploid cells produced

Diploid Haploid

Involved in asexual or sexual reproduction

Asexual Sexual

Results in body cells or sex cells

Body cells Sex cells

Number of divisions involved (one or two)

One Two

28. Complete the chart below comparing the process of Replication, Transcription and Translation.

Replication Transcription TranslationWhere does it

occur?Nucleus Nucleus Cytoplasm

___ making ___ DNA making DNA

DNA making RNA

RNA making Proteins

What molecules are involved in the process? (DNA, mRNA, tRNA, rRNA)

DNA DNA and RNA (mRNA, tRNA, rRNA)

RNA

(mRNA, tRNA, rRNA)