EOCT REVIEWDomain III - Genetics

DNA Deoxyribonucleic acid Made up of nucleotides

Sugar – deoxyriboseA phosphate groupOne of four nitrogen bases

Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

Is in the shape of a double helix

DNA The two strands

are held together by hydrogen bonds between the nucleotides Adenine pairs with

thymine Guanine pairs with

cytosine The order of the

bases is the genetic code

DNA REPLICATION DNA makes an exact copy of itself Takes place in the nucleus

1. An enzyme ‘unzips’ the DNA2. Free nucleotides pair up with the

exposed nucleotides3. This continues until two identical

copies of the DNA molecule are made The two copies each contain one

side from the ‘original’ DNA and one ‘new’ side

RNA Ribonucleic acid 3 differences (from DNA):

Sugar is ribose instead of deoxyribose

Uracil instead of thymineSingle helix instead of a double

helix 3 types of RNA:

Messenger RNA (mRNA)Transfer RNA (tRNA)Ribosomal RNA (rRNA)

TRANSCRIPTION The process of

making RNA from DNA

Occurs in the nucleus

Only one side of the DNA strand is used to make the RNA

TRANSLATION The process of converting the

information on the mRNA into a protein The mRNA carries the message from

the nucleus to the ribosomes, where the proteins are made

The tRNA molecules bring the amino acids to the ribosomesThe 3 base codon on the mRNA

corresponds to a 3 base anticodon on the tRNA

Each codon carries the code for a specific amino acid

THE GENETIC CODE

QUESTION #1 Which of the following shows how information is transformed to make a protein?a. DNA → RNA → proteinb. gene → chromosome → proteinc. cell respiration → ATP → proteind. ATP → amino acid → protein

QUESTION #2 Information on mRNA is used to make a sequence of amino acids into a protein by which of the following processes?a. replicationb. translationc. transcriptiond. transference

GREGOR MENDEL ‘Father of Genetics’ Studied inheritance in pea plants Concluded that each organism

has two genes for each trait – one from mom, one from dad

Genes come in different forms called allelesDominant – the trait that is

expressedRecessive – the trait that is hidden

MENDEL’S LAWS Law of Dominance – the dominant

allele will prevent the recessive allele from being expressed

Law of Segregation – gene pairs separate when gametes are formed, so each gamete has only one allele of each pair

Law of Independent Assortment – different pairs of genes separate independently of each other when gametes are formed

GENETICS VOCABULARY Homozygous – two identical alleles (TT

or tt) Heterozygous – two different alleles (Tt) Monohybrid – genetic cross involving

one trait Dihybrid – genetic cross involving two

traits Genotype – the genetic makeup of the

organism (Tt) Phenotype – the physical appearance of

the trait (tall)

PUNNETT SQUARES

DIHYBRID PUNNETT SQUARE

QUESTION #3 Pea plants have seeds that are either round or wrinkled. In this cross, what will be the phenotypic ratio of the offspring?a. 50% RR and 50% Rrb. 25% RR, 50% Rr, and

25% rrc. 50% round seeds and

50% wrinkled seedsd. 100% round seeds

THE CELL CYCLE Interphase

G1 phase – cell growth

S phase – DNA replication

G2 phase – preparation for mitosis

M phase Mitosis Cytokinesis –

division of the cytoplasm

MITOSIS Division of the nucleus Two identical daughter cells are

produced The chromosome number

remains the same Purpose:

Growth and tissue repairAsexual reproduction

PHASES OF MITOSIS Prophase – the duplicated chromosomes

become visible and spindle fibers form across the cell; the nuclear envelope starts to break up

Metaphase – the chromosomes attach to the spindle and line up randomly in the middle of the cell

Anaphase – the chromosomes are pulled to opposite ends of the cell

Telophase – a nuclear membrane forms around the chromosomes at each end of the cell; spindle fibers disappear; chromosomes become less visible

PHASES OFMITOSIS

QUESTION #4 Why is it important for the cells

of multicellular organisms to undergo mitosis?a. Mitosis allows for reproduction with

male and female gametes.b. Mitosis increases variation within an

organism.c. Mitosis produces cells that are different

from the original dividing cell.d. Mitosis produces identical cells to the

original dividing cell.

MEIOSIS The production of gametes (sex

cells – sperm and eggs) The chromosome number is cut

in half, producing haploid gametesDiploid (2n) – 2 of each

chromosome Normal body cells

Haploid (n) – 1 of each chromosome Sex cells

MEIOSIS There are two divisions

Meiosis I Prophase I – crossing over can occur Metaphase I Anaphase I Telophase I

Meiosis II Prophase II Metaphase II Anaphase II Telophase II

MEIOSIS

GENE MUTATIONS Changes in the nucleotide

sequence of a DNA moleculeSubstitution – a single nucleotide is substituted for another one (A instead of G)

Insertion – a nucleotide is addedDeletion – a nucleotide is removed

A mutation can be harmful, neutral, or beneficial depending on how it affects the protein that is produced

QUESTION #5 What is a source of genetic variation?a. mutationb. adaptationc. replicationd. transcription

GENETIC ENGINEERING Recombinant DNA – inserting foreign

genesHuman insulin is mass produced by

bacteria that have had the human insulin gene inserted

Creates genetically modified organisms Cotton plants have been modified to resist

worm attacksBacteria have been modified to clean up

oil spills, manufacture alcohol, and process minerals

QUESTION #6 Which of the following is the correct base-pairing rule for DNA?a. A-U; C-Gb. A-G; T-Cc. A-T; G-Cd. A-C; T-G

QUESTION #7 A mutagenic factor that can alter DNA by the loss of a chromosome segment is known asa. translocationb. crossing overc. deletiond. nondisjunction

QUESTION #8 In Mendel’s experiments with a single trait, the trait that disappeared in the first generation and reappeared in the next generation is called thea. homozygous traitb. dominant traitc. recessive traitd. heterozygous trait

QUESTION #9 Which of the

following correctly shows the shape of a DNA molecule?

QUESTION #10 Changes to an organism’s DNA can cause unexpected traits to be expressed in its offspring. DNA in an individual’s gametes will most likely be altered before being passed to offspring if exposed toa. x-raysb. loud soundsc. magnetic fieldsd. extreme temperatures

QUESTION #11 Agricultural companies have

developed the ability to control the genetic characteristics of their crops. Genetic engineering techniques have been used to produce all of the following effects excepta. grow salt-tolerant crop plantsb. decrease harvesting timec. make crop plants resistant to diseased. decrease soil nitrogen levels

QUESTION #12 In fruit flies, the gray body color (G) is dominant to the ebony body color (g). What is the genotypic ratio of the offspring of a heterozygous gray female and an ebony male?a. 25% Gg, 75% ggb. 50% Gg, 50% ggc. 75% gray, 25% ebonyd. 100% gray

QUESTION #13 The process of meiosis produces gametes. How does this process increase reproductive variability?a. Different combinations of alleles are

produced.b. Each allele from the parent cell forms a

separate gamete.c. Each pair of genes undergoes crossing-

over with different genes.d. The two genes are passed on to a

daughter cell, resulting in new traits.

QUESTION #14 DNA and RNA are nucleic acids. A characteristic of RNA is that ita. remains in the chromosomes in

the nucleusb. is involved in translating

information in DNA into proteinsc. undergoes crossing-over during

meiosisd. is replicated during the process of

mitosis

QUESTION #15 ATG is a DNA triplet that codes for an amino acid. Which mRNA codon will pair with the ATG tripleta. ATGb. GTUc. TACd. UAC

ANSWERS1. A2. B3. D4. D5. A6. C7. C8. C9. D10. A11. D12. B13. A14. B15. D

INFORMATION AND IMAGES OBTAINED FROM: http://www.doe.k12.ga.us/ci_test

ing.aspx?PageReq=CI_TESTING_EOCT&SubPageReq=GUIDES

Google image search Campbell, Neil A. and Reece Jane

B (2001). "6". Biology. Benjamin Cummings.

Miller, Kenneth R. and Levine Joseph S. (2002). Biology. Prentice Hall.