1a1-chapter 4 genetics and cell function Flashcards Preview

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1

Mendelian genetics

–Gregor Mendel
–investigates family patterns of inheritance

2

Cytogenetics

uses techniques of cytology and microscopy to study chromosomes and their relationships to hereditary traits

3

Molecular genetics

uses biochemistry to study structure and function of DNA

4

Genomic medicine

treatment of genetic diseases through an understanding of the human genome

5

DNA

deoxyribonucleic acid -a long threadlike molecule with uniform diameter, but varied length
46 DNA molecules in the nucleus of most human cells
polymers of nucleotides

6

Each nucleotide consists of

–one sugar -deoxyribose
–one phosphate group
–one nitrogenous base

7

nitrogenous base

•Either pyrimidine(single carbon-nitrogen ring) or purine (double ring)

8

Purines

double ring
–Adenine (A)
–Guanine (G)

9

Pyrimidines

single ring
–Cytosine (C)
–Thymine (T)

10

DNA bases

ATCG

11

DNA Structure

Molecular shape is a double helix(resembles a spiral staircase)
each sidepiece is a backbone composed of phosphate groups alternating with the sugar deoxyribose.

12

Complementary Base Pairing

Nitrogenous bases united by hydrogen bonds
a purine on one backbone with a pyrimidine on the other

13

DNA base pairing

–A –T
–C –G

14

Law of Complementary Base Pairing

–one strand determines base sequence of other

15

Discovery of the Double Helix

Watson, Crick and Wilkins

Rosalind Franklin, who died of cancer

16

Genome

all the genes of one person
•2% of total DNA
•other 98% is noncoding DNA

17

chromatin

fine filamentous DNA material complexed with proteins
occurs as 46 long filaments called chromosomes

18

histones

disc-shaped cluster of eight proteins

19

nucleosome consists of

•core particle –histones with DNA around them
•linker DNA –short segment of DNA connecting core particles

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chromosome territory

permeated with channels that allow regulatory chemicals to have access to the genes

21

Cells Preparing to Divide

•exact copies are made of all the nuclear DNA
•each chromosome consists of two parallel filaments of identical DNA -sister chromatids
•in prophase, final coiling and condensing
final compaction enables the two sister chromatids to be pulled apart and carried to separate daughter cells without damage to the DNA

22

RNA

RNA much smaller cousin of DNA (fewer bases)
•one nucleotide chain (not a double helix as DNA)
•ribose replaces deoxyribose as the sugar
•uracil replaces thymine as a nitrogenous base

23

RNA Types

3

–messenger RNA (mRNA) over 10,000 bases
–ribosomal RNA (rRNA)
–transfer RNA (tRNA) 70 -90 bases

24

RNA Essential function

–interprets code in DNA
–uses those instructions for protein synthesis
–leaves nucleus and functions in cytoplasm

25

Current Definition –gene-

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

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Genome

all the DNA in one 23-chromosome set
46 human chromosomes comes in two sets of 23 chromosomes

27

Human Genome Project

(1990-2003)
identified the nitrogenous base sequences of 99% of the human genome

28

genomics

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

29

Findings of Human Genome Project

Homo sapiens has only about 25,000 to 35,000 genes

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Genetic Code

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

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Base triplet

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

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codon

the 3 base sequence in mRNA
64 possible codons available to represent the 20 amino acids

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Stop Codons

UAG, UGA, and UAA–signal the „end of the message‟, like a period at the end of a sentence

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Start Codon

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

35

Overview of Protein Synthesis

-a mirror-image copy of the gene is made
•migrates from the nucleus to cytoplasm
•its code is read by the ribosomes
(tRNA) –delivers amino acids to the ribosome
–ribosomes assemble amino acids in the order directed by the codons of mRNA

36

activated gene - process

messenger RNA (mRNA)
ribosomes
transfer RNA (tRNA)

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messenger RNA (mRNA)

a mirror-image copy of the gene is made
•migrates from the nucleus to cytoplasm
•its code is read by the ribosomes

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ribosomes

cytoplasmic granules composed of ribosomal RNA (rRNA) and enzymes
–ribosomes assemble amino acids in the order directed by the codons of mRNA

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transfer RNA (tRNA)

delivers amino acids to the ribosome

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Summary of Protein Synthesis

process of protein synthesis
DNA --- mRNA --- protein

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transcription

step from DNA to mRNA
copying genetic instructions from DNA to RNA
–occurs in the nucleus where DNA is located

42

translation

step from mRNA to protein
–most occurs in cytoplasm
–15-20% of proteins are synthesized in the nucleus

43

RNA Polymerase

enzyme that binds to the DNA and assembles the mRNA

44

terminator

base sequence at the end of a gene which signals polymerase to stop

45

pre-mRNA

immature RNA produced by transcription

46

exons

“sense” portions of the immature RNA
–will be translated to protein

47

introns

introns–“nonsense” portions of the immature RNA
–must be removed before translation

48

alternative splicing

removing the introns by enzymes and splicing the exons together into a functional RNA molecule
–one gene can code for more than one protein

49

translation

the process that converts the language of nucleotides into the language of amino acids

50

ribosomes

translate sequence of nucleotides into the sequence of amino acids

51

leader sequence

mRNA molecule begins with leader sequence
acts as binding site for small ribosomal subunit
when start codon (AUG) is reached, protein synthesis begins

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all proteins begin with ________________ when first synthesized

methionine

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transfer RNA (tRNA)

requried for translation
–small RNA molecule
–coils on itself to form an angular L shape
–one end of the L includes three nucleotides called an anticodon

54

polyribosome

one mRNA holding multiple ribosomes
cell can produce 150,000 protein molecules per second

55

Peptide Formation

6 steps

-DNA double helix
-Seven base triplets on the
template strand of DNA
-The corresponding codons of
mRNA transcribed from the
DNA triplets
-The anticodons of tRNA that
bind to the mRNA codons
-The amino acids carried by
those six tRNA molecules
-The amino acids linked into a
peptide chain

56

Protein Processing and Secretion

•protein synthesis is not finished when the amino acid sequence (primary structure) has been assembled.
•to be functional it must coil or fold into precise secondary and tertiary structure

57

Chaperone proteins

–older proteins that pick up new proteins and guides the new protein in folding into the proper shapes
–helps to prevent improper association between different proteins

58

Chaperone proteins also called

also called stress proteins or heat-shock proteins

59

Protein Packaging and Secretion

6 steps

-Protein formed by ribosomes on rough ER
-Protein packaged into transport vesicle, which buds from ER.
-Transport vesicles fuse into clusters that unload protein into Golgi complex
-Golgi complex modifies protein structure
-Golgi vesicle containing finished protein is formed
-Secretory vesicles release protein by exocytosis.

60

Protein Processing

•proteins to be used in the cytosol are likely to be made on free ribosomes in cytosol
•proteins destined for packaging into lysosomes or secretion from the cell are assembled on rough ER and sent to Golgi complex for packaging

61

posttranslational modification

Happens in ER
–removing some amino acid segments
–folding the protein
–stabilizing protein with disulfide bridges
–adding carbohydrates

62

Gene Regulation

•genes are turned on and off from day to day
•their products are needed or not
•many genes are permanently turned off in any given cell

63

Synthesizing Compounds Other Than Proteins

cells synthesize glycogen, fat, steroids, phospholipids, pigments, and other compounds
–no genes for these
–synthesis under indirect genetic control
–produced by enzymatic reactions
–enzymes are proteins encoded by genes

64

DNA Replication and Cell Cycle

•before cells divide, it must duplicate its DNA so it can give a complete copy of all its genes to each daughter cell.
•since DNA controls all cellular function, this replication process must be very exact

65

Law of Complementary Base Pairing

we can predict the base sequence of one DNA strand if we know the sequence of the other
–enables a cell to reproduce one strand based on the information in another

66

Steps of DNA Replication

first 3

-Double helix unwinds from histones
-.enzyme DNA helicase opens one short segment of helix at a time - replication fork
- DNA polymerase molecules move along each strand and the two separated strands of DNA are copied by separate polymerase molecules proceeding in opposite directions

67

Steps of DNA Replication

last 5

- DNA ligase joins segments
-from the old parental DNA molecule, two new daughter DNA molecules are made
-semiconservative replication
-new histones are synthesized in cytoplasm

68

replication fork

the point where the DNA is opened up (like two separated halves of a zipper)

69

semiconservative replication

each daughter DNA consists of one new helix synthesized from free nucleotides and one old helix conserved from the parental DNA

70

mutations

changes in DNA structure due to replication errors or environmental factors (radiation, viruses, chemicals)
–some mutations cause no ill effects. others kill the cell, turn it cancerous or cause genetic defects in future generations.

71

cell cycle

the cell‟s life cycle that
extends from one division to the next

72

cell cycle

4 phases

G1 phase,
S phase,
G2 phase,
M phase,

73

G1 phase,

the first gap phase
–interval between cell division and DNA
replication
–accumulates materials needed to replicate DNA

74

S phase,

synthesis phase
–duplicates centrioles
–DNA replication occurs

75

G2 phase,

second gap phase
–interval between DNA replication and cell division
–finishes centriole duplication
–synthesizes enzymes that control cell division
–repairs DNA replication errors
92 DNA MOLECULES

76

M phase,

mitotic phase
–cell replicates its nucleus
–pinches in two to form new daughter cells

77

Interphase

collection of G1, S, and G2phases

78

G0(G zero) phase

cells that have left the cycle for a “rest”
–muscle and nerve cells

79

Mitosis

•cell division in all body cells except the eggs and sperm
•Functions of mitosis
–development of the individual from one fertilized egg to some 40 trillion cells
–growth of all tissues and organs after birth
–replacement of cells that die
–repair of damaged tissues

80

4 phases of mitosis

prophase, metaphase, anaphase, telophase

81

Prophase

Chromosomes condense and nuclear envelope breaks down. Spindle fibers grow from centrioles. Centrioles migrate to opposite poles of cell.

82

Metaphase

Chromosomes are aligned on cell equator
–oscillating slightly and awaiting signal that stimulates each of them to split

83

mitotic spindle

lemon-shaped array of spindle fibers
–long spindle fibers (microtubules) attach to chromosomes
–shorter microtubules (aster) anchor centrioles to plasma membrane at each end of cell

84

Anaphase

•activation of an enzyme that cleaves two sister chromatids apart at centromere
•daughter chromosomes migrate towards each pole of the cell with centromere leading the way

85

Telophase

•chromatids cluster on each side of the cell
•rough ER produces new nuclear envelope around each cluster
•chromatids begin to uncoil and form chromatin
•mitotic spindle breaks up and vanishes
•each nucleus forms nucleoli

86

Cytokinesis

the division of cytoplasm into two cells
•achieved by motor protein myosin pulling on microfilaments of actinin the terminal web of cytoskeleton
•creates the cleavage furrow around the equator of cell
•cell eventually pinches in two

87

Cells divide when:

•they have enough cytoplasm for two daughter cells
•they have replicated their DNA
•adequate supply of nutrients
•are stimulated by growth factor
•neighboring cells die, opening up space in a tissue to be occupied by new cells

88

Cells stop dividing when:

•snugly contact neighboring cells
•when nutrients or growth factors are withdrawn
•contact inhibition –the cessation of cell division in response to contact with other cells

89

growth factor

chemical signals secreted by blood platelets, kidney cells, and other sources

90

contact inhibition

the cessation of cell division in response to contact with other cells

91

heredity

transmission of genetic characteristics from parent to offspring

92

karyotype

chart of 46 chromosomes laid out in order by size and other physical features

93

homologous chromosomes

the two members of each pair of the 23 pair

94

the two members of each pair

22 pairs
look alike and carry the same genes

95

sex chromosomes

one pair of sex chromosomes (X and Y)
–normal female has homologous pair of X chromosomes
–normal male has one X and one much smaller Y chromosome

96

diploid

any cell with 23 pairs of chromosomes (somatic cells)

97

haploid

contain half as many chromosomes as somatic cells –sperm and egg cells (germ cells)

98

fertilization

fertilization restores diploid number to the fertilized egg and the somatic cells arise from it.

99

locus

the location of a particular gene on a chromosome

100

alleles

different forms of gene at same locus on two homologous chromosomes

101

dominant allele

(represented by capital letter)
–corresponding trait is usually detectable in the individual
–masks the effect of any recessive allele that may be present
–produces protein responsible for visible trait

102

recessive allele

(represented by lower case letter)
–expressed only when present on both of the homologous chromosomes
–no dominant alleles at that locus

103

genotype

the alleles that an individual possesses for a particular trait

104

homozygous alleles

two identical alleles for a trait

105

heterozygous alleles

different alleles for that gene

106

phenotype

an observable trait
–an allele is expressed if it shows in the phenotype of an individual

107

genetic counselors

perform genetic testing or refer clients for tests, advise couples on the probability of transmitting genetic diseases, and assist people on coping with genetic disease

108

Punnett square

shows how 2 heterozygous parents with cleft chins can have child with uncleft chin

109

gene pool

collective genetic makeup of population as a whole

110

multiple alleles

more than two allelic forms for a trait

111

codominant

both alleles equally dominant

112

incomplete dominance

phenotype intermediate between traits each allele would have produced alone

113

Sex-linked traits

carried on the X and Y chromosomes, and therefore tend to be inherited by one sex more than the other

114

Penetrance

the percentage of a population with a given genotype that actually exhibits the predicted phenotype

115

Role of environment

gene can produce a phenotypic effect without nutritional and other environmental input

116

benign tumor

–slow growth
–contained in fibrous capsule
–will not metastasize
–usually easy to treat

117

malignant tumor

called cancer
–fast growing
–metastasize–give off cells that seed the growth of multiple tumors elsewhere

118

metastasize

give off cells that seed the growth of multiple tumors elsewhere

119

Oncology

medical specialty that deals with both benign and malignant tumors

120

tumor angiogenesis

ingrowth of blood vessels stimulated by energy-hungry tumors

121

carcinomas

originate in epithelial tissue

122

lymphomas

originate in lymph nodes

123

melanomas

originate in pigment cells of epidermis (melanocytes)

124

leukemias

in blood forming tissues

125

sarcomas–

in bone, other connective tissue, or muscle

126

carcinogen

environmental cancer-causing agents
–radiation –ultraviolet rays, X-rays
–chemical-cigarette tar, food preservatives, industrial chemicals
–viruses–human papilloma virus, hepatitis C, and type 2 herpes simplex

127

Oncogenes

causes cell division to accelerate out of control

128

Tumor suppressor genes

inhibit development of cancer

129

cachexia

severe wasting away of depleted tissues

130

allo-

different

131

dactylo-

finger

132

diplo

double

133

haplo-

half

134

hetero-

different

135

karyo-

nucleus

136

meta-

next in a series

137

morpho-

shape

138

muta-

change

139

poly-

many

140

kinetochore

protein plaques on either side of the centromere

140

Mutations

3 types

List