ch. 4 genetics and cellular function

Question 1

DNA structure and function

deoxyribonucleic acid (DNA)

Answer 1

long-thread like molcule with uniform diameter, but varied length
* 46 DNA molecules (chromosomes) in nucleus of most human cells
avg human DNA molecule about 2 in long

Question 2

DNA structure and function

DNA and other nucleic acids are polymers of

Answer 2

nucleotides
* nucleotide consists of a sugar, phosphate group, and nitrogenous base

Question 3

DNA structure and function

a single nucleotide

Answer 3

• one sugar- deoxyribose
• one phosphate group
• one nitrogenous base
  purines-double ring
  Adenine (A)
  Guanine (G)
  pyrimidines-single ring
  Cytosine (C)
  Thymine (T)
  Uracil (U)

DNA bases A, T, C, G

Question 4

DNA structure and function

double helix shape of DNA (resembles spiral staricase)

Answer 4

• each sidepiece is a backbone of phosphate groups alternating with deoxyribose
• step-like connections between the backbones are pairs of nitrogen bases

Question 5

DNA structure and function

nitrogenous bases united by hydrogen bonds

Answer 5

• a purine on one strand always bound to a pyrimidine on the other
• A-T two hydrogen bonds
• C-G three hydrogen bonds

Question 6

DNA structure and function

DNA base pairing

Answer 6

• A-T
• C-G

Question 7

DNA structure and function

law of complimentary base pairing

Answer 7

one strand determines base sequence of other

Question 8

DNA structure and function

gene

Answer 8

a segment of DNA coding for the synthesis of a specific protein

Question 9

DNA structure and function

genome

Answer 9

all the genes of one person
* humans have about 20,000 genes

only about 2% of total DNA
other 98% is noncoding DNA

    plays role in chromosome structure
	    regulation of gene activity

Question 10

chromatin and chromosomes

chromatin

Answer 10

fine filamentous DNA material complexed with proteins
* occurs as 46 chromosomes in most cells
* 6 ft long thread packed in cell nucleus of 5 diameter
* in nondividing cells, chromatin is so slender it cannot be seen with light microscope
* granular appearance under electron microscope

Question 11

chromatin and chromosomes

histones

Answer 11

proteins crucial for DNA packing
* histones cluster in groups of 8 molecules
* DNA molecule winds around the cluster (like thread around spool)
* chromatin consists of thousands of repeating nuclesomes

Question 12

chromatin and chromosomes

nucleosome consists of

Answer 12

• core particle–histone cluster with DNA around it
• linker DNA–short segment of DNA connecting core particles

nucleosomes zigzag like an accordian

Question 13

chromatin and chromosomes

chromatin thrown into

Answer 13

complex, irregular loops and coils
* 1,000 times shorter than original molecule

Question 14

chromatin and chromosomes

each chromosome is packed into its own region of the

Answer 14

nucleus–chromosome territory
* permeated with channels allowing regulatory chemicals to have access to the genes

Question 15

chromatin and chromosomes

in a nondividing cell the chromatin is NOT

Answer 15

static
* changes moment to moment according to a genetic activity of cell
* genes get turned off and on
Example: during development, chromosomes migrate, so that
genes on different chromosomes can partner to bring about
developmental changes in the cell

Question 16

Chromatin and Chromosomes

when preparing to divide cell makes copy of all

Answer 16

nuclear DNA

Question 17

Chromatin and Chromosomes

each chromosome then consists of 2

Answer 17

parallel filaments of identical DNA–sister chromatids

becomes visible with light microscope

Question 18

Chromatin and Chromosomes

chromatide are joined at

Answer 18

constricted centomere
* kinetochores–protein plaques on each side of centromere

Question 18

RNA strucute and function

ribonucleic acids (RNAs)

Answer 18

smaller molecules that resemble DNA
* can have less than 100 or just over 10,000 bases per molecule

Question 19

RNA strucute and function

3 importanr RNAs for protein synthesis

Answer 19

• messenger RNA (mRNA)
• ribosomal RNA (rRNA)
• transfer RNA (tRNA)

Question 20

RNA strucute and function

RNA structure

Answer 20

• one nucleotide chain (not a double helix)
• ribose replaces deoxyribose as the sugar
• uracil replaces thymine as a nutrogenous base
• functions mainly in CYTOPLASM

Question 21

what is a gene?

previous definition of gene

Answer 21

a segment of DNA that carrier the code for a particular protein
* but body has millions of proteins and only about 20,000 genes

Question 22

What Is a Gene?

Current definition: gene

Answer 22

an information-containing segment
of DNA that codes for the production of a molecule of RNA that plays a role in synthesizing one or more proteins

Amino acid sequence of a protein is determined by the
nucleotide sequence in the DNA
©

Question 23

What Is a Gene?

Genome

Answer 23

all the DNA in one 23-chromosome set
* 3.1 billion nucleotide pairs in human genome

Question 24

What Is a Gene?

46 human chromosomes come in two sets of

Answer 24

23
chromosomes
* One set of 23 chromosomes came from each parent

Question 25

What Is a Gene?

Genomics

Answer 25

study of the whole genome and how its genes
and noncoding DNA interact to affect structure and function
of the whole organism

Question 26

What Is a Gene?

home sapiens has fewer than

Answer 26

100,000 genes

Question 27

What Is a Gene?

a single gene can code for many different

Answer 27

proteins

Question 28

What Is a Gene?

a gene is on avg

Answer 28

3,000 bases long

can be up to 2.4 million bases long

Question 29

What Is a Gene?

all humans are at least 99.99% genetically

Answer 29

identical
* still 2 individuals can differ by more than 3 million base pairs
* combinations of single-nucleotide polymorphins account for all human genetic variation

Question 30

what is a gene

some chromosomes are gene ____ and some are gene ____

Answer 30

gene-rich
gene-poor

Question 31

what is a gene

currentlt we know locations of over 1,400

Answer 31

disease-producing mutation
* opens possibilities of genomic medicine

Question 32

the genetic code

body can make millions of different proteins (the proteome) from just 20

Answer 32

amino acids and encoded by genes made of just four nucleotides
(A, T, C, G)

Question 33

the genetic code

genetic code

Answer 33

a system that enables these 4 nucleotides to code for amino acid sequences of all proteins

Question 34

the genetic code

minimum code to symbolize 20

Answer 34

amino acids is 3 nucleotides per amino acid

Question 35

the genetic code

base triplet

Answer 35

a sequence of 3 DNA nucleotides that stands for 1 amino acid

Question 36

the genetic code: base triplet

codon

Answer 36

3-base sequence in mRNA

Question 37

the genetic code: base triplet

64 possible codons available to represent the 20

Answer 37

amino acids

Question 38

the genetic code: base triplet

61 code for

Answer 38

amino acids

Question 39

the genetic code: base triplet

3 codons are

Answer 39

stop codons

Question 40

the genetic code: base triplet

stop codons

Answer 40

UAG
UGA
UAA
signal “end of message”

like a period at the end of the sentence

Question 41

the genetic code: base triplet

start codon

Answer 41

AUG codes for methionine
begins the amino acid sequence of the protein

Question 42

protein synthesis

all body cells except sex cells and some immune cells contain

Answer 42

identical genes

Question 43

protein synthesis

different genes are activated in

Answer 43

different cells

Question 44

protein synthesis

any given cells uses 1/3 to 2/3 of its genes

Answer 44

the rest remain dormant and may be functional in other types of cells