Biology Chapter 7 HMK: DNA Structure and Replication

Identify the statements that describe the structure of DNA.

- A DNA double helix contains two sugar‑phosphate backbones oriented in opposite directions - Adenine is paired with thymine, and guanine is paired with cytosine - The five‑carbon sugar of DNA is called deoxyribose

DNA replication is said to be semiconservative, which means that a newly replicated, double-stranded DNA molecule consists of which components?

- One new strand - One old strand

What reagents are needed for a typical polymerase chain reaction (PCR)?

- Template DNA - 2 primers - Taq polymerase - 4 nucleotides (A, T, C, G)

DNA evidence can give an investigator information regarding which of the following?

- The identity of an individual based on a profile - Family relationships between suspects

Using DNA profiling, DNA from a blood sample collected at a crime scene can be compared to DNA from a blood sample taken from a suspect. The DNA profile will show whether the blood from the crime scene belongs to the suspect. Arrange the steps in the order needed to create a DNA profile from the two blood samples.

1. Extract the DNA from the cells in each blood sample 2. Use PCR to amplify specific repeated DNA sequences that were cut from the DNA sample with restriction enzymes 3. Put the two sets of DNA fragments on a gel, and use electrophoresis to separate each set of fragments by length 4. Compare the DNA fragment lengths of crime scene blood and suspect's blood.

Label the indicated components of the DNA double helix.

1. Major groove 2. Minor groove 3. Nitrogenous bases 4. Phosphodiester bonds

Order the events that occur in one cycle of the polymerase chain reaction (PCR).

1. The reaction mixture is heated to 94C 2. The double-stranded DNA is denatured to form single-stranded DNA 3. The temperature of the reaction mixture is lowered to allow the primers to anneal to the DNA template. 4. The reaction mixture is heated to 72C 5. Taq polymerase synthesizes a new DNA strand

Suppose Jenni has a PCR product that contains three DNA fragments of 300300, 700700, and 10001000 base pairs in length. She separates the three fragments using gel electrophoresis. Which fragment will migrate the farthest from the wells at the top of the gel?

300bp fragment

The _____ chromosomes in a human cell from inside the cheek are found in the _____ .

46; nucleus

If you start with one copy of a DNA fragment, how many rounds of PCR will it take to end up with a total of 32 copies?

5

Which phrase best describes chromatin?

A fiber composed of DNA and protein molecules

What is short tandem repeat (STR) analysis?

A procedure that compares the lengths of short, repeated DNA regions across samples

In a human DNA sample, you detect DNA that is specifically from the X chromosome. Why are you unable to definitively determine the sex of that person (male or female) from the presence of the X chromosome?

Both males and females have an X chromosome, and you would have to check for the presence of a Y chromosome.

A DNA molecule consists of two polynucleotide strands that form a double helix. The strands are held together by hydrogen bonds between the nitrogen‑containing bases. One strand is complementary to the other strand, which means that a base on one strand is paired with a base on the opposite strand. The nucleotide bases in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T). Choose the DNA sequence complementary to GACT.

CTGA

This substance is made up of fibers that are formed in the nucleus by supercoiling genetic material

Chromatin

What are the structures in a cell that group genes together, are composed of chromatin (DNA and protein), and become visible under a light microscope during mitosis?

Chromosomes

Which description best describes the function of chromosomes?

Compact DNA, facilitating proper distribution during cell division

What is the key feature of DNA that allows it to be copied?

Complementary base pairing

This series of nucleotides encodes proteins

DNA

DNA is wrapped around histone proteins and coiled to form a dense fiber called chromatin. Which statement describes the function of the chromatin conformation of DNA?

DNA is wrapped around histone proteins to condense and organize DNA.

Which enzyme pairs corresponding nucleotides to a preexisting DNA chain in order to synthesize a new strand of DNA?

DNA polymerase

Which statement about PCR is true?

DNA polymerase is the enzyme that copies DNA in PCR

What naturally occurring process does PCR mimic in a test tube?

DNA replication

Which scenario describes sequencing?

Determining the order of nucleic acids in a DNA molecule

The three-dimensional structure of DNA is shown in the interactive. What is the shape of DNA molecules?

Double helical

What is the shape of DNA molecules?

Double helical

Which of these are nucleotides found in DNA?

Four types: adenine (A), guanine (G), cytosine (C) and thymine (T)

Which STR will have migrated farthest through an electrophoresis gel?

GAAG repeated twice

What is the purpose of the polymerase chain reaction (PCR)?

Generate copies of a piece of DNA

The entire sequence of DNA in a cell used for DNA profiling is called the

Genome

When copying a DNA sequence during PCR, the two original strands of the DNA molecule are separated by _____ ; then the enzyme _____ "reads" each template strand and adds _____ to make a new strand.

Heat; DNA polymerase; complementary nucleotides

Which enzyme separates the two complimentary strands of DNA during DNA replication?

Helicase

These proteins regulate transcription and modifications of genetic material

Histones

What intermolecular force is responsible for holding the two strands of a DNA double helix together?

Hydrogen bonds

Why is Taq polymerase used as the DNA polymerase in the polymerase chain reaction (PCR)?

It is thermodynamically stable at the temperature used to separate the DNA strands

Which scientist created the Nobel‑prize winning polymerase chain reaction (PCR)?

Kary Mullis

In the polymerase chain reaction (PCR), early replication errors affect a larger percentage of PCR products than late replication errors. Select the reason why this occurs.

Less DNA in early cycles results in a higher overall proportion of copies containing the error because each round uses the fragment from earlier rounds as templates

Human red blood cells are enucleated (i.e., they do not have nuclei). Is it possible to isolate DNA from red blood cells? Why or why not?

No, because the genomic DNA is found only in nucleated cells

Specialized proteins associate with DNA in the nucleus, forming DNA-protein complexes. What is the term for a segment of DNA wrapped around a core of eight proteins?

Nucleosome

What is the monomer that makes up DNA?

Nucleotides

An individual's STR may differ from the same STR of another individual by the

Number of times a particular sequence is repeated

Before DNA synthesis begins, a short RNA nucleotide sequence that is paired to a template strand of DNA must be synthesized. What is the name of that RNA nucleotide sequence?

Primer

What is the purpose of careful primer design before PCR?

Primers indicate the section of DNA that will be amplified and mark where DNA polymerase begins replication.

This folded amino acid chain is genetically encoded and performs specific functions in cells

Protein

What are the components of eukaryotic chromosomes?

Protein and DNA

From the STRs used in a forensic investigation, which STRs on which chromosomes would be particularly useful in determining whether crime scene evidence was left by a female or a male?

STR's on the Y chromosome

Gel electrophoresis separates DNA for profiling based on the

Size (length

How are DNA fragments separated using gel electrophoresis?

Smaller DNA fragments move through the gel more quickly than larger‑fragments

DNA has unique properties that allow it to accurately retain genetic information, even after multiple rounds of replication. One aspect of DNA that allows it to accurately store genetic information is the base pairing from Chargaff's first rule of the four nucleotide bases. If the A content of a DNA molecule is 22%,22%, what are the percentages of the remaining bases?

T = 22% G = 28% C = 28%

If the sequence of one strand of DNA is AGTCTAGC, what is the sequence of the complementary strand?

TCAGATCG

Which of these describes a genome?

The collection of genetic material in a cell or organism

Which phrase represents genetic variation between individuals?

The number of STR's in their genomes

How does the structure of DNA encode genetic information?

The sequence of bases

Which person would have DNA that is least similar to yours?

Your mother's brother