DNA - Exam 2

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What is DNA made up of ?

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Exam 2

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What is DNA made up of ?

nucleotides

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What are the 3 parts to a nucleotide ?

phosphate group (1-3), deoxyribose sugar, nitrogenous base

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Which type of base has a double ring structure ?

purines

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Which type of base has a single ring structure ?

pyrimidines

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What are the 5 nitrogenous bases and which is found in DNA or RNA?

adenine, thymine (DNA), guanine, cytosine, uracil (RNA)

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What make deoxygenated-ATP different from THE ATP?

missing OH group on sugar

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How many phosphate groups can be attatched to a DNA nucleotide?

1-3

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What is the difference in deoxyribose sugar (DNA) and ribose sugar (RNA)?

deoxyribose has H on 2 carbon spot, ribose has OH on 2 carbon spot

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Which nitrogenous bases are purines?

adenine and guanine

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Which nitrogenous bases are pyrimidines?

thymine, uracil, cytosine

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What makes thymine different from uracil?

thymine has methyl group (CH3)

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What type of bond links nucleotides?

phosphodiester bonds

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Is the linkage of nucleotide (phosphodiester linkage) energetically favorable?

unfavorable because of condensation rxn (covalent bond)

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1’ =

nitrogenous base

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3’ =

hydroxyl group

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5’ =

phosphate group

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What is considered the “top” end of DNA and what is always dangling off it?

5’ end; phosphate group always dangling off

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What is considered the “bottom” end of DNA and what is the always dangling off it?

3’ end; hydroxyl group always dangling off (OH)

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Number such as 5’ and 3’ refer to ?

carbon atoms in sugar ring

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What are the two sources of nucleotides?

de novo synthesis and salvage pathway

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What is the de novo synthesis?

cutting and pasting from acid or carbohydrate pieces

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What and where are nucleotides synthesized?

synthesized by enzymes in cytoplasm and transport to nucleus

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What is the salvage pathway?

old nucleotides are fixed up

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Which process of making nucleotides is preferred?

salvage pathway (conserves energy)

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What happens to nucleotides that cannot be used in salvage pathway?

nucleotide is broken down into uric acid; eliminated

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What is leech-nyan syndrome?

X-linked disorder caused by mutation in HGPRT gene (deficiency in HGPRT gene)

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What does HGPRT gene do?

makes enzyme needed to recycle purine nucleotides

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What happens in the lesch-nyhan syndrome when there is no HGPRT gene?

uric acid is overproduced; causing arthritis, mental disability, hypotonia (weak muscles)

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Does a patient of lesch-nyhan have enough DNA?

yes, symptoms are a result of uric acid accumulated in tissues

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What causes Alzheimer’s disease?

tau protein hyper-phosphorylation

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What do tau protein do to neuronal cells?

stabilize the microtubules (skeletons of neuronal cells)

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What does hyperphosphorylation do to tau proteins?

tau drops off and forms tangles, destabilizing the microtubules

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Phosphorylated tau also causes ?

chronic traumatic encephalopathy (CTE)

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How does phosphorylated tau cause CTE?

repeated blows to head, brain remembers everytime hit

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? is important in dephosphorylating proteins

alkaline phosphatase

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When there is a phosphatase deficiency, ? occurs

hypophosphatasia, where bones and teeth are not mineralized (soft bones)

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When a protein becomes denatured, ? begin to break and unfolds

H bonds

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What are the 4 causes of denaturation?

heat, changes in pH, salt concentration, solvent

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Denaturation is not always ?, it depends on method and what denaturatued

permanent

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What are the two reasons for cooking?

denature bacterial/fungal proteins and break food molecules down to conserve energy

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How else can food be denatured besides cooking?

prolonged exposure to acid in lemon, lime, or tequila (usually fish)

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Normal pH of vagina is ?

3.8-4.2

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How does sperm survive acidic vaginal environment?

sperm contains buffers that protect it from the acidity of vagina

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Are A-T bonds stronger, weaker or the same strength as G-C bonds?

G-C bonds are stronger with 3 H-bonds

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Why is DNA double stranded?

A-T and C-G pair via H-bonds

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DNA is ? as a single strand

unstable

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The two strands in DNA are ? meaning ?

antiparallel, running in opposite directions

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When calculating percentages of A,T,G, and C in DNA…

A=T and G=C

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What is the percentage of uracil in DNA strand?

0%

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Complementary base pairing forms what shape?

double helix

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The major grooves are ? and the minor grooves are ? in a double helix structure

major=wider, minor=narrow

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DNA is ? and the distance between sugar phosphates differ

asymmetrical

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What is the double helix structure most similar to?

staircase, proteins able to grip nitrogenous bases easier

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How many bases are in each turn?

10.4

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What is an ester bond?

C-O

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Where do most protein contact interactions occur?

major groove

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How many H-bonds does it take to stabilize G-C pair?

3 bonds

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How many H-bond does it take to stablize A-T pair?

2 bonds

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What does A-T pair having only 2 H-bonds allow for more easily?

easier to seperate 2 bonds for transcription and replication

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Which direction are nucleotide sequences are read?

5’ to 3’ (left to right)

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The 5’ end is always ?

top left

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The 3’ end is always ?

bottom right

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What types of cells have NO cell wall?

animal and fungal cells

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Where is DNA kept in a eukaryotic cell?

mitochondria (most DNA HERE) and nucleus

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What is DNA packaged as?

chromosomes (linear)

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What is a karyotype?

organized profile of all chromosomes

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What are the 3 structure needed to make a chromosome in any eukaryotic organisms?

telomere, replication origin, centromere

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What is a replication origin?

w/o this cannot pass on from mother to daughter cell, usually several

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What is a centromere?

where mitotic spindle attaches, usually 1

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What is a telomere?

caps at the ends of chromosomes, usually 2

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Are eukaryotic chromosomes haploid or diploid?

diploid (2 copies of each)

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What are homologous chromosomes?

same length, bonding pattern, gene order, but sequence of DNA is not identical

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Which human chromsomes are not (always) homologous?

X and Y (sex chromosomes)

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What are human chromosomes of males?

XY (Y is smaller)

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What are the human chromosomes of females?

XX

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What does the SRY gene do in the Y chromosome?

stimulate testes development and testerone production

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What humans’ sex during the first stages of development?

female

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What is swyer syndrome?

XY individuals who have defects in their testosterone production, have uterus, vagina, no ovaries

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What are the 3 possible defects of testosterone production?

SRY gene damaged; has SRY gene, but not producing testosterone; produce testosterone, but cannot recept it

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How can individuals with swyer syndrome become pregnant?

hormone therapy or donor embryo implantation

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What is the zygote that they believed Foekje Dillema had and what did divide into?

XXY and divided into a mosaic of XX and YY cells

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What is a mosaic?

when a person has more than 1 genotype

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What is XXY ?

Kleinfelter’s condition, usually in men that have feminized features, smaller size, more body fat (inital 47 chromosomes)

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What does intersex mean?

having characteristics of human male and female phenotypes

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