nucleus, genes, dna Flashcards
what does the nucleus contain
- contains the genetic material of the cell in the form of DNA - deoxyribonucleic acid
what are 4 structures of the nucleus
- double phospholipid membrane
- nuclear envelope which contains nuclear pore
- nucleolus
- membrane is continuous with other membranes that form the ER
what is the function of the nuclear pore and structure of nuclear pore
- allows things into the nucleus - mainly proteins needed for DNA replication and transcription
- allows things out such as RNA - requires atp
- nuclear envelope contains nuclear pore
- ring of protein and anchor protein which hold the rings of protein in the nuclear envelope
what is the nucleolus and its functions and what are ribosomes
- nucleolus is where the ribosomes, required for protein synthesis are assembled
- ribosomes are a mixture of rna and proteins
what does dna contain
- dna contains all the information required to produce and maintain all the components of a cell
what are the four bases
- adenine
- thymine
- guanine
- cytosine
what are each of the bases bonded to and what is it termed
- each base is bonded to a deoxyribose
- each of these are termed nucleoside
what is each nucleoside bonded to and what is it termed
- each nucleoside is bonded to a phosphate
- each termed as nucleotide
what do the nucleotides form
- form a phosphate backbone
what does the sequence of the four nucleotides determine
- determines the sequence of every protein in the cell, which determine the function of the cell
explain anti parallel chain
- two strands of nucleotides line up opposite each other with each string going in opposite directions
- one going 5’ - 3’ and the other going 3’ - 5’
- the structure of the bases only allow adenine to be opposite thymine and guanine to be opposite cytosine
- this allows the maximum amount of bonds to be formed
what is double helix and what does this result in
- the two strands are coiled into a double helix
- this gives stability
- the bases are protected by the sugar phosphate backbone
- very long
why do dna strands coil up and what is formed
- dna molecule is v big
- so it coils up more, wrapped around proteins called histones forming a nucleosome
- nucleosomes coils up forming solenoid
- all together this is termed chromatin
in dividing cells what happens to chromatin
- chromatin condenses further around scaffold proteins to from chromosomes
how many chromosomes does each human diploid cell have
- 46 chromosomes termed 2n
- 22 pairs of of chromosomes (autosomal) plus 2 sex chromosomes
what are the steps involved when a cell is preparing to divide
- dna needs to be replicated (dna replication)
- it is done by small sections of dna unwinding to form ‘bubbles’ that allows the enzyme DNA polymerase to copy each of the strands of DNA
- the new strand of DNA is then paired with its template parental dna strand and separates into the new daughter cell
- semi conservative replication
- DNA polymerase are proof reading enzymes therefore able to correct errors
what is a gene
encodes for a protein
what are egg and sperm cells termed as
- haploid cells, n
what do diploid cells contain
- two copies of each chromosome and therefore each gene
what are two copies of genes called
- alleles
what are alleles significant in
- disease and inheritance
explain transcription
- section of dna around the gene must be unwound
- this separates the strand
- allowing rna polymerase to get in and synthesise a strand of rna
- with a sequence complimentary to that of the template dna strand
- this produces mrna which is then used as the template for synthesising the protein
what happens to the introns and how is the mrna modified
- spliced out and a cap and tail are put on it
- the resulting mature transcripts are then exported from the nucleus through the nuclear pores
- 5 prime cap - chemical structure is added to one end - interacts with nuclear pore
- on other end poly a tail attached
explain transcription
- mature rna translated into proteins by ribosomes
- strings of amino acids are formed by specific transfer rna
- recognising three base codons on the mature mrna
- each codon specifies a trna molecule covalently bound to a specific amino acid
what is a stop codon
- do not code for amino acids therefore stopping translation
- peptide bonds form between the amino acids bound to the trna forming a polypeptide and when a stop codon is reached the polypeptide is released
what happens when dna is mutated
- mutated dna results in mutated rna therefore mutated protein
- results in disease due to genetic or chromosomal abnormalities
oral cancer
- associated with mutation or changes in expression of genes
- causes cells to divide abnormally therefore leading to a tumour
4 uses of dna in medicine
- diagnostics
- prognostics
- forensics
- treatment
structure of rna
- single stranded
- formed by transcription from dna
- involved in protein synthesis
- sugar, base, phosphate
- ribose sugar
- thymine replaced with uracil
what are the three forms of rna
- rRNA (ribosomal)
- tRNA (transfer)
- mRNA (messenger)
what is rna called that is not coded into proteins
- non coding rna
role of enzyme helicase
- causes dna to unwind
role of DNA polymerase
- joins unwound strand - brings opposite bases
