Biology

mutations do occur

1 mistake per billion is good, but does generate mutations. environmental factors also damage DNA and creat mutations. damaged DNA is often repaired, but not always

5 basic types of mutations

3 small scale mutations (one or few bases) they are nucleotide substitution (point mutation), insertion, deletion, ( 2 large scale mutations (big chunks of DNA)) inversion, and translocation

details about DNA molecules

DNA molecules is a double helix double= two connected chains (strands) of nucleotides like a ladder helix-two strands twist like a circular staircase

history of the search for DNA's structure

James Watson and Francis Crick were developing a 3-D model of DNA but was missing something critical. Maurice Wilkins and Rosalind Franklin had x-ray pictures of DNA. they combined information which led to the discovery of DNA structure

so the complimentary strand of A A C C G A T looks like

T T G G C T A

3 parts nucleotides are...

a phosphate group (PO4), a monosaccharide ribose for RNA and deoxyribose for DNA, and a nitrogenous bas (base)

inversion

a piece of DNA is cut out and then replaced in the wrong direction

nucleotide substitution

a single base pair is altered

need to replicate DNA

as cells divided, the DNA they contain must be accurately passed on to both daughter cells. it's done by, before dividing, a cell produces two identical of all its DNA, one copy for each daughter cell

the backbone and rungs of the ladder

backbone of the strands is sugar-phosphate groups of nucleotides bonded each other. covalent bonds is strong. two strands run in opposite direction, anti-parallel

the DNA code

blue eyes, tall, and allergies relates to the sequence (order) of bases along the chain

are mutations good or bad

both and neither. some mutations have no effect (neutral) and some mutations lead to new versions of genes that work better and some mutations inactive or change crucial genes-harmful or lethal effects.

DNA replication is semiconservative

cells build 2 new strands of DNA from scratch that pair up with each of the 2 old strands. when compare the new double strands twist into helix. the 2 new double helictites are 1/2 old DNA and 1/2 new DNA. both should be identical

mutations are

changes in the sequence of DNA. mistakes can be made during the DNA replication process but DNA replication process has features that reduce mutations

environmental factors that could damage DNA are

chemicals (burning plants, industrial), low wavelengths waves (x-rays and ultraviolet)

concept of heredity

concept that offspring resemble parents has been recognized for centuries

scientific method and history of search for genes

discovery- chromosomes in the nucleus of cells were always copied before cell divided (reproduced). by 1900's scientists knew chromosomes were composed of DNA and proteins. work 1940's -1950's confirmed that genes were found on the DNA

genes are (old definition)

discrete "units" of information passed on to offspring by parents

science behind heredity

due to Mendel and others, by mid 1800's we knew that the thing that is passed on from parent to offspring are called genes

DNA replication... how does it work

enzymes called DNA helical ex break the hydrogen bonds and pull the two strands apart, unzips the double helix. each strand now has a backbone and half of each rung sticking out, unpaired. enzymes called DNA polymerases escort free nucleotides (free A, G,...) to each strand and match them to make new pairs. the sugar/phosphate portions of the new free nucleotides are also joined to make a new backbone

what is DNA

is a type of nucleus acid (organic). RNA is another type.made up of chains of nucleotides (basic unit)

sickle cell anemia

mutation in the gene that makes hemoglobin, a blood protein. hemoglobin gene is 438 bases long. 1 substitution at the 17th bases (T-----A becomes A-----T)

mistakes are called

mutations.

correcting mistakes during DNA replication

newly replicated DNA is proofread for errors. repair enzymes repair errors that are found. uncorrected error rate for DNA replication is about 1 mistake per billion base pairs copied

the bases found in DNA

nucleotides uses four bases: adenine (A), guanine (G), thymine (T), and cytosine (C). the whole nucleotides if often just referred to its base

insertion

one or a few base pairs are added into the sequence

deletion

one or few bases pairs are removed from the sequence

translocation

one or more pieces of DNA are removed and inserted into a different place (often another chromosome)

DNA replication is called

semiconservative