Chapter 4: Genes and Genetic Diseases Flashcards Preview

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Flashcards in Chapter 4: Genes and Genetic Diseases Deck (21)
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1
Q

What are the basic units of inheritance?

A

Genes

2
Q

What are genes composed of?

A

Sequences of deoxyribonucleic acid (DNA)

3
Q

What are histones?

A

A protein constituent of DNA that causes it to coil into a highly compressed structure.

4
Q

How many genes do humans have?

A

20,000 to 25,000

5
Q

What is the genotype?

A

The composition of genes at a given locus

6
Q

What is the phenotype?

A

The outward appearance of an individual, which is the result of both genotype and environment

7
Q

What are polypeptides?

A

Intermediate protein compounds, which are in turn composed of sequences of amino acids.

8
Q

What are amino acids?

A

organic acids containing NH2

p. 137

(this is ammonia with one of its hydrogen atoms removed; also called amidogen)

9
Q

The body contains ___ different types of amino acids.

A

20

10
Q

What are the subunits of DNA?

A

nucleotides

11
Q

Each nucleotide contains:

A

one pentose sugar (deoxyribose)

one phosphate group

one nitrogenous base (either cytosine, thymine, guanine, or adenine)

12
Q

How does DNA direct the formation of certain amino acids?

A

each amino acid is specified by a triplet of nitrogenous bases called codons.

13
Q

How many possible codons are there? (each codon is a triplet and there are 4 kinds of nitrogenous bases)

A

4 x 4 x 4 = 64

14
Q

What is the structure of DNA? (p. 136)

A

A double helix; envision a twisted ladder with weak hydrogen bonds as the rungs

15
Q

What enzyme is the most important in the process of DNA replication?

A

DNA polymerase

16
Q

What are mutagens? (p. 140)

A

agents which are known to increase the frequency of mutations (ex: radiation)

17
Q

Describe the basic steps of DNA replication.

A

The DNA strand is untwisted and unzipped. A single strand acts as a template.

DNA polymerase pairs the complementary bases; adenine with thymine, and cytosine with guanine.

DNA polymerase adds new nucleotides and “proofreads” the new protein; if not correct, the incorrect nucleotide is excised and replaced.

18
Q

What is the estimated mutation rate in humans?

A

10 ^ -4 to 10 ^ -7 per gene per generation.

19
Q

What are 2 primary differences between DNA and RNA?

A

Uracil rather than thymine is present in RNA. (Uracil pairs with adenine.) Also, RNA usually occurs as a single strand rather than a double like DNA. (p. 141)

20
Q

DNA is formed and replicated in the ____ _______, protein synthesis take place in the _________.

A

Cell nucleus

Cytoplasm

21
Q

What fraction of pediatric inpatients are children with genetic diseases?

A

one-third

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