DNA ReplicationBiology II

Bell Ringer Questions/Exit QuestionsExplain “Diploid” Explain “Haploid” What is the difference between Somatic vs. Sex Cells?

DNA is made up of what?

DNA ReplicationBefore a cell divides, it duplicates its

DNA in a process called replicationReplication=DNA copies itself exactlyOccurs with in the nucleus

Any mistakes in copying=mutation

DNA Replication1. Complementary Base Pairing: makes replication possible

makes replication possible C - G

A - T

DNA Replication2. One side of the DNA molecule is a

template for making the other (strand)

Nitrogen BasesReplication Fork

Original strandNew Strand

Growth

Growth

DNA ReplicationDNA replication is carried out by enzymes

that “unzip” the DNA called helicaseHydrogen bonds between base pairs are

broken and the two strands of DNA unwind

DNA ReplicationThe principal

enzyme involved in DNA replication is DNA polymeraseJoins individual

nucleotides to produce a DNA molecule

Proofreads each strand

Semi-conservative ReplicationEach new DNA

molecule contains one old strand and one new strand

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12–2

In prokaryotic cells, DNA is found in the

a. cytoplasm.

b. nucleus.

c. ribosome.

d. cell membrane.

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Slide 11 of 21

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The first step in DNA replication is

a. producing two new strands.

b. separating the strands.

c. producing DNA polymerase.

d. correctly pairing bases.

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Slide 12 of 21

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A DNA molecule separates, and the sequence GCGAATTCG occurs in one strand. What is the base sequence on the other strand?

a. GCGAATTCG

b. CGCTTAAGC

c. TATCCGGAT

d. GATGGCCAG

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Slide 13 of 21

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In addition to carrying out the replication of DNA, the enzyme DNA polymerase also functions to

a. unzip the DNA molecule.

b. regulate the time copying occurs in the cell cycle.

c. “proofread” the new copies to minimize the number of mistakes.

d. wrap the new strands onto histone proteins.

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The structure that may play a role in regulating how genes are “read” to make a protein is the

a. coil.

b. histone.

c. nucleosome.

d. chromatin.

RNA and Protein Synthesis

RNA Structure and FunctionGenes are coded DNA instructions

that control the production of proteins.Genetic messages can be decoded by copying part of the nucleotide sequence from DNA to RNA

RNA contains coded information for making proteins

DNA vs. RNADifferences:

The sugar in RNA is ribose instead of deoxyribose

RNA is single strandedRNA contains uracil (U) in place of Thymine (T)

Structure of RNA1. Phosphate Group2. Ribose sugar3. Nitrogen Containing Bases

a) Cytosine (C)b) URACIL (Not Thymine) (U)c) Adenine (A)d) Guanine (G)

3 Types of RNAThere are 3 types of RNA, each with a

specific function:

1. Messenger RNA (mRNA): A straight RNA molecule that carries a complimentary copy of a gene.

A. The complementary copy of a gene (found on DNA) is called the genetic code (found on the mRNA)

B. The genetic code is read 3 bases at a time (AUG, GGA, etc) which are called codons

**Brings instructions indicating which amino acids will be needed and in which order they will be bonded together.

3 Types of RNA2. Transfer RNA (tRNA): A folded RNA

molecule that is t-shapedB. At the top of the tRNA molecule is the site

where amino acids (protein monomers) attach.

C. At the bottom of the tRNA molecule is the site where the genetic code is read

**Brings amino acids to the ribosome!

3 Types of RNA3. Ribosomal RNA (rRNA): a folded globular

shaped molecule ***Site of Protein Synthesis

A G C T T C G C A G G C C A T