DNA Flashcards
What is the structure of DNA
-nucleotides
-deoxyribose (sugar) and a phosphate backbone
-weak hydrogen bonds between bases
-nitrog. bases: cytosine, thymine, guanine, adenine
-make two chains that twist into a spiral shape known as a double helix
-DNA strands wrap around special proteins called histones to form nucleosome which later are known as chromatin or chromosome depending on the cells dividing properties
found in cell nucleus and mitochondria
What is a chromatin?
Tangled network formed from coiled DNA
What makes up chromosomes? How many are in a somatic cell?
46
-made up of tightly coiled chromatin that go through cell division
What is the difference between mitochondrial DNA and nuclear DNA?
Mitochondrial:
-small circular molecules
-not bound by proteins
Nuclear
-long double helix structure
-bound by proteins(histones)
What is a nucleosome made of?
DNA wrapped around eight histone proteins
What are some similarities between transcription and DNA replication
-occur in the nucleus
-rely on enzymes in order to occur
-make complementary strands using nucleotides A, C, G, and T or U
-DNA is used as a template
-The new strand is synthesized 5’-3’
What is translation?
the production of a protein using the information that is coded in the mRNA molecule
How does translation occur?
-in the cytoplasm
-a ribosome, along with tRNA, attaches to one end of the mRNA molecules
-tRNA’s and ribosomes then move along mRNA 3 bases at a time (codon), reading them as it goes
-when tRNA, carrying corresponding anticodons to the mRNA’s codons, and ribosome reaches the starting codon, it translates that genetic code into a specified string of amino acids
-folds to form protein
What is transcription?
The process by which the mRNA is formed using the code in a DNA molecule
How does transcription occur?
-the DNA’s genetic instruction are replicated or transcribed to the mRNA molecule
-the enzyme RNA polymerase make double sided DNA strand come apart
-RNA polymerase then transcribe bases of one strand=complementary mRNA molecule
-at the end of gene-sequence of bases that tell RNA polymerase to stop copying=mRNA molecule release
-the introns are removed leaving the exons
-the functional mRNA will leave nucleus and direct protein synthesis in the cytoplasm
How does protein formation occur?
transcription and translation
What is a gene?
An inherited strait factor that codes for a specific protein
What is an allele?
Alternative form of a gene
Define dominant
An allele that masks the effect of another allele
e.g. A and B or I
Define recessive
Allele that is masked by the alternative, dominant allele
e.g. 0 and i
Define homozygous
The situation where an individual has the same alleles for a particular characteristic i.e. pure breeding
Define heterozygous
The situation where an individual possesses different alleles for a particular characteristic i.e. hybrid
Define phenotype
The physical appearance of an individual as determined by the expression of the alleles for that characteristic
Define genotype
The genetic make-up of an individual as determined by the alleles for the characteristic being considered
Define Punnett square
Means of calculating the probability of genotypes and phenotypes of offspring
Define pedigree
Family tree/register recording a line of ancestors
What is RNA’s structure?
-made up of nucleotides, which are ribose sugars attached to nitrogenous bases and phosphate groups
- nitrogenous bases include adenine and uracil as well as , guanine, uracil, and cytosine
Causes of variation
- crossing over
- non-disjunction
- random/independent assortment
- random fertilisation
What occurs during ‘crossing over’?
Occurs in meiosis
Legs of homologous chromosome become tangled and DNA is exchanged increasing genetic variety
e.g. brothers and sisters having differing traits
