GENETICS 1 Flashcards
what is a phenotype
this is the outward and physical manifestation of an organism
what is a genotype
this is the full hereditary information of an organism even if not expressed .
what is the relationship between DNA structure an d function
DNA is transcribed into mRNA and then translated into proteins in the ribosome .
what is the structure of a DNA
made up of a pentose sugar , phosphate group and a nitrogenous base .
what is a nucleoside
a base and a pentose sugar
bonds involved in a DNA molecule
there is hydrogen bonds that are formed between the nitrogenous bases.
what are purines
they are adenine and guanine
what are pyrimidines
they are thymine , cytosine and uracil in the RNA .
complementary base pairing the number of bonds that are formed
3 bonds for cytosine and guanine
2 bonds for adenine and thymine
the largest organelle in animal cells
the nucleus which contains the DNA
site for DNA replication
nucleus
site for DNA transcription
nucleolus
what are chromosomes
they are wound DNA that are packed together into a thread like structure.
length of the DNA
2m
what are the parts of a chromosome
the two sister chromatids that are joined together by the centromere.
how many chromosomes are present in a human cell
humans have 23 pairs of chromosomes with 22 pairs being autosomal while 1 pair the 23rd being sex chromosome
how does the DNA achieve the structure to be able to be packaged into a chromosome.?
they are tightly wound on histone proteins to form a nucleosome
what is a nucleosome
DNA that is wound around a histone protein.
what does a nucleosome comprise of
comprises of eight histone proteins around which the DNA wraps 1.65 times
chromatin
mixture of DNA ,(histone) proteins and RNA which package within the nucleus.
heterochromatin
the condensed regions of the chromatin
euchromatin
the extended form of the chromatin that is exposed and less wound
process of DNA transcription and replication
1.both require the unzipping and closure of the DNA helix structure this is done by the enzyme ligase and the enzyme helicase.
2. the histone wrapping at the nucleosome has to be altered to expose more genes for the processes.
3. this is done by the addition of other molecules.
4.this is a reversible process .
modifications of the histone
addition of a methyl group
addition of an acetyl group on the histone