Upgrade to remove ads
Only $35.99/year

Biology DNA

Terms in this set (59)

DNA
(deoxyribonucleic acid) a complex molecule/polymer containing the genetic information that makes up the chromosomes. Present in all organisms, usually within the nuclei of cells.
Different in each individual except identical twins.
What are the 3 parts of DNA?
organic polymer (nucleic acid) made up of repeating nucleotides, each consisting of 3 parts:
1. sugar (deoxyribose)
2. phosphate
3. one of four nitrogen bases (Adenine, guanine, cytosine, thymine)
purines
A class of nucleotides that includes adenine and guanine; nitrogenous bases that have two rings of carbon and nitrogen atoms
pyrimidines
A class of nucleotides that includes Thymine, Cytosine, (and Uracil for RNA); nitrogenous bases that have a single ring of carbon and nitrogen atoms
What scientists are credited for the structure of DNA?
in 1953 Watson and Crick called their model of DNA a double helix. They won a nobel prize in 1962
Rosalind Franklin
contributed much to the discovery of the DNA structure with her x-ray photographs
Describe the structure of DNA
double-stranded, twisted molecule; ladder-like molecule. phosphate groups and sugar (deoxyribose) form the sides of the ladder and nitrogen bases form the rungs of the ladder
What type of bond holds together the phosphates and sugars in the ladder sides of DNA?
covalent bonds
What type of bond holds together the nitrogen bases (rungs) of DNA?
weaker hydrogen bonds
What kind of bond does adenine form with thymine?
double bond
What kind of bond does cytosine form with guanine?
triple bond
Chargaff's rule
[A]=[T] and [G]=[C], they pair up across from one another forming two strands also called base pairing.
equal amounts of adenine bonds with thymine and equal amount of guanine bonds with cytosine.
DNA replication
when DNA copies its code into another molecule of DNA, so that cells can divide and both cells have the full complement of DNA
What are the three steps in DNA replication?
Step 1: DNA "unzips", strands separate
Step 2: free DNA nucleotides from the nucleus base pair on both sides of the DNA molecule
Step 3: covalent bonds form between the sugars and phosphates of the 2 new strands, hydrogen bonds form between the nitrogen base pairs for both molecules
helicases
Enzymes that break the hydrogen bonds between the nitrogen base pairs
replication fork
the Y shaped point which forms where the 2 strands of DNA separate, parent (old) strands are on the outside, daughter (new) strands are on the inside
DNA polymerase
enzyme that joins individual nucleotides to produce a DNA molecule, which is a polymer. This proofreads the strands for miss paired nucleotides, making sure the bases pair correctly.
DNA ligase
an enzyme that links the nucleotides together like glue;
helps form the hydrogen bonds between the nitrogen base pairs
What are the 2 parts of protein synthesis?
transcription and translation
transcription
making mRNA from DNA; takes place in the nucleus
What are the 4 steps in transcription?
step 1: DNA separates, RNA polymerases separate the DNA molecule
step 2: free-floating RNA nucleotides within the nucleus attach to corresponding DNA bases on one side of the DNA molecule
step 3: covalent bonds form between the sugars and phosphates on the mRNA strand
step 4: mRNA molecule is released and DNA "zips" back up
Which DNA bases pair with which RNA bases?
DNA-RNA
adenine-uracil
thymine-adenine
cytosine-guanine
guanine-cytosine
What do RNA polymerases do?
they are enzymes that guide transcription by reading the DNA code
translation
using mRNA (messenger RNA) to make proteins, occurs at the ribosomes
What does the order of the bases determine?
it determines which amino acids get lined up and which proteins get made
codon
3 mRNA nucleotides (or bases)
anti-codon
3 tRNA nucleotides (or bases)
anticodons are specific, tRNA (transfer RNA)will only bring a certain amino acid to ribosomes
EX. CCA= glycine only
start codon
AUG (methionine), cause ribosomes to start translating mRNA
stop codon
UAG, UAA, or UGA; signals ribosomes to stop translation
What are the 3 steps in translation?
step 1: mRNA leaves nucleus and travels to ribosomes. AUG causes ribosomes to start translating mRNA
step 2: amino acids are brought to the ribosome by tRNA;
the tRNA bases pair with the mRNA bases
step 3: amino acids join together by a peptide bond to form a protein (polypeptide). A stop codon signals the end of translation
Which mRNA bases pair with which tRNA bases?
adenine-uracil
uracil-adenine
cytosine-guanine
guanine-cytosine
What are the differences between DNA and RNA?
1. DNA has thymine, while RNA has uracil
2. The sugar in DNA is deoxyribose, the sugar in RNA is ribose
3. DNA is 2 stranded, RNA 1 strand
4. DNA stays in the nucleus, RNA can travel between nucleus and cytoplasm
5. there is one type of DNA, there are 3 types of RNA
What is the importance of RNA?
together with DNA, it is involved in protein synthesis, mRNA takes the code out to the ribosomes and tRNA brings amino acids to the ribosomes to make proteins
mutation
a permanent change in DNA caused by mutagens; mutations may occur at different times in the life cycle of an individual
Name some examples of mutagens.
viruses, high temps, chemicals, radiation, etc
How do mutations that occur in eggs and sperm or just after fertilization affect an organism?
All of the cells of the organism will be affected. These mutations will be inherited by the organism's offspring.
Ex. Down's syndrome
How do mutations that occur during the embryonic stage affect an organism?
At the embryonic stage, cells and tissues are differentiating , so only some of the cells of the organism will have the mutation
How do mutations that occur after an organism is fully formed affect an organism?
they affect only the cells in which they occur and their daughter cells (cells that mutated cells give rise to)
Ex. many forms of cancer
mutations which occur in body cells other than sex cells will leave the gene pool when the organism dies
What are the 2 categories of mutations?
gene mutations and chromosomal mutations
gene mutations
produce changes in a single gene (genes smaller than chromosomes and are found on them)
also called point mutations
chromosomal mutations
produce changes in whole chromosome
either the structure of a chromosome changes or an entire chromosome is gained or lost
what are the 2 types of gene mutations?
substitution and frame shifts (insertions and deletions)
substitution
When a base (or a few bases) is substituted in place of the original base.
What 3 things can occur in substitution?
1. changes the amino acid being coded for and therefore the protein
2. changes the amino acid to or from a start or stop codon 3. it may not change the amino acid or protein at all
frame shift
when there are insertions (additions) or deletions (subtractions) of one or more bases.
Much more severe than substitution because it affects more amino acids and everything from the insertion/deletion onward is affected (they shift the "reading frame" of the genetic message).
What are the types of chromosomal mutations?
inversion, translocation, deletion, duplication, nondisjunction
inversion
when a piece of a chromosome breaks off and reattaches to the same chromosome in a reverse orientation; there is no loss of genetic info
What is the most common inversion seen in humans?
occurs on chromosome #9; it is generally considered to have no harmful effects, but there is some suspicion that it could lead to an increased risk for miscarriage or infertility
translocation
when a chromosome segment breaks off and attaches to a different chromosome. Can cause sterility or miscarriages and some cancers. More common in plants.
deletion
the loss of a piece of a chromosome du to chromosome breakage. Small deletions are likely to be fatal, large deletions are usually fatal. Medium sized deletions lead to recognizable disorders such as William's syndrome
duplication
produces an exact copy of a portion of a chromosome, wide variety of effects, can cause autism and certain types of cancer
nondisjunction
When a pair of chromosomes fail to separate correctly during meiosis (production of sex cells)
trisomy
A condition in which 3 chromosomes rather than a pair occur. Down syndrome is caused by trisomy by the addition of an extra chromosome to the 21st chromosome pair.
kleinfelter's syndrome
male with more than one X chromosome (XXY)
monosomy
A condition in which only one of a pair of chromosomes is present, as in Turner's Syndrome, when there is only one X-chromosome, instead of the usual two.
genetic engineering
the application of molecular genetics for practical purposes. Examples: medicine (insulin), cures for diseases, gene therapy, criminal cases, agriculture
DNA fingerprinting
a pattern of bands made up of specific fragments of a person' s DNA. Banding patterns of DNA are compared to establish relatedness. Can be used to solve crimes or prove paternity
DNA fingerprinting steps
1. collect sample and isolate DNA. Only a small amount of tissue like blood, hair or skin is needed.
2. DNA is cut using restriction enzymes. It is cut at specific places. EX. an enzyme called EcoR1, found in bacteria, will cut DNA only when the sequence GAATTC occurs.
3. Fragments of DNA are separated using gel electrophoresis
4. Transfer of DNA to nylon. A nylon sheet is placed on the gel and soaks overnight
5. Probing. adding radioactive or colored probes to the nylon sheet produces a pattern called the DNA fingerprint
6. DNA fingerprints are compared
gel electrophoresis
fragments are sorted according to size
samples of DNA being compared are loaded into wells in a porous gel then an electric current is run through the gel
DNA is negatively charged and moves toward the positive charged end of the gel
smaller DNA fragments move faster and will travel further along the gel
Sets with similar terms