#3 DNA/RNA

51問 • 1年前

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In 1953, _____ noted that DNA consists of two polynucleotide strands, running in opposite directions and coiled around each other in a double helix

Watson and Crick

Strands are held together by ______ between specific pairs of bases

hydrogen bonds

The strands of DNA are complementary because of

H-bonding

The primary structure of a nucleic acid is the ______

nucleotide sequence

The nucleotides in nucleic acids are joined by ______

phosphodiester bonds

The 3’-OH group of the sugar in one nucleotide forms an ______ to the phosphate group on the 5’-carbon of the sugar of the next nucleotide

ester bond

A ________ has a free 5’-phosphate group at one end and a free 3’-OH group at the other end The sequence is read from the free 5’-end using the letters of the bases This example reads 5’—A—C—G—T—3’

nucleic acid polymer

In DNA, A, C, G, and T are linked by________ between deoxyribose and phosphate

3’-5’ ester bonds

is described from 5' end, identifying the bases in order of occurrence, using the abbreviations A for adenosine, G for guanosine, C for cytidine, and T for thymine (or U for uracil in RNA) A typical sequence is written as

chain, TAGGCT

Properties of a DNA double helix

The strands of DNA are antiparallel, The strands are complimentary, There are Hydrogen bond forces, There are base stacking interactions, There are 10 base pairs per turn

Secondary Structure

DNA double helix

In DNA there are two strands of nucleotides that wind together in a double helix - the strands run in ______ - the bases are are arranged in ______ - the base pairs are held together by _______

opposite directions step-like pairs hydrogen bonding

The pairing of the bases from the two strands is very specific. The complimentary base pairs are A-T and G-C Each pair consists of a purine and a pyrimidine, so they are the same width, keeping the two strands at equal distances from each other

two hydrogen bonds form between A and T three hydrogen bonds form between G and C

The model was developed by Watson and Crick in 1953.

DNA model

Watson and Crick received a nobel prize in _____ for their work.

1962

The dna model looks like a twisted ladder – ______

double helix

- Columbia University, NY -Investigated the composition of DNA -His findings by 1950 strongly suggested the base-pairings of A-T & G-C

Erwin Chargaff – (1905-2002)

Met with Watson and Crick in _____ and shared his findings

1952

A = T & C = G

Chargaff’s rule

First determined by Watson & Crick in 1953

Nucleic Acid Structure (the double helix)

Shape and size is uniform for all life (i.e. DNA is identical)

TRUE

Without parallel base pairing this conformation could not exist

FALSE

Nucleic acid structure consists of

major” grooves and “minor” grooves

are critical for binding proteins that regulate DNA function

Major grooves

The paired strands are coiled into a spiral called

DOUBLE HELIX

[normally] exists as a single stranded polymer

RNA

exists as a double stranded polymer

DNA

DNA double strand is created by _______ between nucleotides

hydrogen bonds

Nucleotides always bind to

complementary nucleotides

1. Before a cell divides, the DNA strands unwind and separate 2. Each strand makes a new partner by adding the appropriate nucleotides 3. The result is that there are now two double-stranded DNA molecules in the nucleus. When the cell divides, each nucleus contains identical DNA

Replication

STEP 1: Hydrogen bonds between base pairs are broken by the ________ and DNA molecule unzips. DNA molecule separates into complementary halves

enzyme Helicase

Cell division involving ______ produces 2 daughter cells that are genetically identical to each other and genetically identical to the parent cell

mitosis

Remember that for this (replication) to happen, DNA in the parent cell must be replicated (copied) before the cell divides – this process occurs during ______ in the cell cycle

Interphase

STEP 2: ______ match up with complementary bases. Free nucleotides abundant in nucleus

Nucleotides

Nucleotides are linked into 2 new strands of DNA by the enzyme, ________—_______ also proofreads for copying errors

DNA polymerase

occur when copying errors cause a change in the sequence of DNA nucleotide bases

Mutations

In eukaryotic cells (animals, plants, fungi) DNA is stored in the nucleus, which is separated from the rest of the cell by a

semipermeable membrane

The DNA is only organized into _______ during cell replication

chromosomes

Between replications, the DNA is stored in a compact ball called ______, and is wrapped around proteins called ________ to form nucleosomes

chromatin, histones

When a eukaryotic cell divides, the process is called _____ - the cell splits into two identical daughter cells - the DNA must be replicated so that each daughter cell has a copy

mitosis

DNA replication involves several processes: 1. - first, the DNA must be _____, separating the two strands

unwound

DNA replication involves several processes: 2. - the ______ then act as templates for synthesis of the new strands, which are complimentary in sequence

single strands

DNA replication involves several processes: 3.- bases are added one at a time until two new DNA strands that exactly duplicate the _______ are produced

original DNA

A process where one strand of each daughter DNA comes from the parent DNA and one strand is new

semi-conservative replication

The energy for the synthesis of the new strands comes from _______ of phosphate groups as the phosphodiester bonds form between the bases

hydrolysis

Schematic representation of the strand separation in duplex DNA resulting from its

heat denaturation

unwinds several sections of parent DNA

enzyme helicase

open DNA section, called a

replication fork

_____ catalyzes the formation of 5’-3’ester bonds of the leading strand

DNA polymerase

The _______, which grows in the 3’-5’ direction, is synthesized in short sections called ______

lagging strand, ozaki fragments

The Okazaki fragments and ______ are joined by to give a single 3’-5’ DNA strand

DNA ligase

CH 1

OBILLO, MIKAELA T. · 78問 · 1年前

CH 1