Genetics Test 1- slide set 1

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1

1850s – 1940s Genetics

- Started with Mendel and Darwin, something is inherited

– Comparing mutants with wild-type

– Mapping

2

Watson and Crick

-1953

-what is a gene

-described the structure of double-stranded DNA as a double helix.

-right-handed (clockwise)

- anti parallel (opposite polarity)

3

Transmission genetics

classical genetics, heredity, how genes and traits are transmitted from generation to generation

4

Molecular genetics

what genes are, the molecular structure and function of the genetic material, how genes are expressed; genomics

5

Quantitative genetics

how traits are inherited that are determined by multiple genes

6

Population genetics

the distribution and behavior of genes in populations (usually one gene per trait)

7

Sarccharomyces cerevisiae

yeast

8

Drosophilia melanogaster

fruit fly

9

Caenorhabiditis elegans

nematode

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Arabidopsis thaliana

mustard weed family

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Mus musculus

house mouse

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Homo sapiens

humans

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Neurospora crassa

orange bread mold

14

Tetrahymena

protozoan

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Paramecium

protozoan

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Chlamydomonas reinharditii

green alga

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Pisum sativum

garden pea

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Zea mays

corn

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Danio reio

zebrafish

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Gallus

chicken

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E. coli

bacterium

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Prototrophic

strains can grow on minimal growth media and synthesize other organic molecules that are needed

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Auxotrophic

mutants do not grow on minimal media and require supplements; specifically they need the molecule they cannot synthesize

24

DNA

-sugar is deoxyribose, bases are ACGT

- Nucleus, cytoplasm; Mitochondrion, chloroplast

- transcribed, producing RNA

25

RNA

- sugar is ribose, bases are ACGU

- Nucleus, cytoplasm; Mitochondrion, chloroplast

- reverse transcribed, producing DNA

– translated, producing a polypeptide

26

How is DNA expressed?

-Different genes – alleles

-Genotype + environment = phenotype

27

How DNA changes

– Experimental recombination

– Natural recombination; prokaryotes, eukaryotic meiosis

– Mutation

28

What is the monomer of DNA and RNA

Monomer = nucleotide

29

Structure of DNA

- Pentose sugar

- bases

- phosphate group PO4 2-

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Pentose sugar

- Learn structures of ribose and deoxyribose

– 5’ carbon is outside of the ring

– OH = hydroxyl group

31

Phosphate group PO42 forms what type of bond and where?

– Forms phosphodiester bond between 3’ carbon of one sugar and 5’ carbon of the next

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Polarity of the chain

is characterized by the phosphate group on a 5' carbon at one end and the hydroxyl group on the 3' carbon at the other end

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Purines

- Adenine

- Guanine

- 9 member double ring

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Pyrimidines

- Cytosine

- Thymine

-Uracil

- 6 member single rings

35

What is base pairing?

The bonds between nitrogenous bases in the DNA double helix

36

Covalent bond between is where in the DNA sugar?

N and 1' carbon

37

Chargaff's rule

-bases are 50% purines and 50% pyrimidines

- (A+G)/(C+T)=1

- A+T/C+G may vary

38

What type of bonds are between G? +A/G, and how many are between the purines and pyrimidines?

-hydrogen bonds

- 3 bonds of C+G

-2 bonds A+T

39

A-DNA

bases are more inclined, helix wider, 11 base pairs per turn. Major (deep) groove is narrow and minor (shallow) is wide.

40

B-DNA

Distances above describe B-DNA, normal under hydrated conditions (although DNA in cells may be a little more twisted).

41

Z-DNA

indicates zigzag sugar-phosphate backbone. Left-handed helix with 12 base pairs per turn. Unknown role.

42

RNA specialties

Single-stranded RNA will fold up with secondary structure forming regions of double-stranded RNA separated by unpaired regions

43

What is the genome size?

haploid

44

Relative genome sizes of viruses, prokaryotes, and eukaryotes

Viruses=103-105 bp

Prokaryotes – 106 (or 1+ Mb)

Eukaryotes – most 108-109

45

Organization of DNA in viruses, prokaryotes, and eukaryoktes

viruses- varies

prokaryotes- usually single circular chromosome, double-stranded DNA

eukaryotes- usually multiple linear

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exonuclease

cleaves at the end

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endonuclease

cleaves in the middle

48

sticky ends

lambda phage is double-stranded DNA single linear chromosme with single-stranded complementary ends

49

T2, T4, T6

double stranded DNA single linear chromosome

50

ΦX174

single-stranded DNA single circular chromosome

51

Influenza

segmented single-stranded RNA

52

Prokaryotic chromosomes

If multiple chromosomes, usually one main chromosome and others are smaller. If the smaller chromosomes are dispensable, they are called plasmids

53

Plasmids

multiple smaller chromosomes that are displensable

54

DNA is compacted because:

Positive and negative supercoiling – supercoiled vs. relaxed DNA controlled by topoisomerases (enzymes found in all organisms)

55

Looped domains

ends of looped regions are held in place so that each region can be supercoiled

56

Eukaryotic chromosomes

-The number of chromosomes is characteristic of the species.

-Karyotype = complete set as in metaphase

- All eukaryotes have similarly structured chromatin

57

Chromatin

the stain-able material consisting of the DNA in a chromosome plus the proteins (about twice as much as DNA) complexed with it.

58

Histones and non histones

-histones are generally small and positively charged; about as much histone as DNA by weight

- nonhistones vary greatly at different stages of cell cycle, organism, and are negatively charged binding to histones

59

Nucleosomes

bead-like regions of DNA compacted by histone binding

60

When are chromosomes most compact?

during mitosis and meiosis, least compacted during S stage of interphase when replication occurs.

61

Centromeres

-important in cell division, these regions are where the mitotic or meiotic spindle fibers attach

-multiple proteins bind to these regions, forming the kinetochore where the end of the microtubule attaches

62

telomeres

important in DNA replication, these regions are at the end of the chromosome and provide stability

63

telomere extreme ends

-contain a short repeated sequence that differs between species

- associated sequences can extend thousands of bp in from the ends

64

Unique-sequence

-Unique means that the haploid genome has a single copy or few copies of the sequence

-Usually genes regions (coding for proteins) are unique or repeat only a few times, but not all unique-sequence DNA is coding

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Repetitive-sequence

- Moderately

-Highly (>105 copies)

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Prokaryotes sequences

-Unique: most of the genome

– Moderately repetitive: rRNA and tRNA (due to level of expression)

67

Eukaryotes sequence

-55-60% of human genome is unique-sequence

– If repetitive sequences repeat many times in a row, they are called tandem repeats

(Some are long and associated with genes, like regions coding for tRNA and rRNA • Some are as short as 1-10 bp • Most common are in centromeres and telomeres)

68

Eukaryotic repetitive sequences

families of similar repetitive sequences may be spaced at irregular intervals (dispersed)

69

LINES

long interspersed elements 1-7 kb

70

SINES

short interspersed elements 100-400 bp

71

LINES and SINES in repetitive sequences

they make up a large part of the moderately repetitive sequences

72

Transposons

full-length LINE-1 sequences

(represents about 15% of the mammalian genome)