chapter 8- DNA, genes and protein synthesis Flashcards
(28 cards)
what is a gene and what does it code for?
it is a base sequence of DNA which codes for
- the amino acid sequence in a polypeptide
-a functional RNA (rRNA/ tRNA)
how many bases make up an amino acid?
3
what can codons be describes as and why?
they can be describes as degenerate due to more that one code being able to code for an amino acid
what does DNA and RNA stand for?
deoxyribonucleic acid and ribonucleic acid
RNA structure
single stranded made up of nucleotides with bases A, U, C, G. ribose sugar and a phosphate group
what are the three types of RNA involved in protein synthesis
messenger RNA/ mRNA
ribosomal RNA / rRNA
transfer RNA/ tRNA
What is messenger rRNA
a long single stranded molecule formed into a helix, manufactured in the nucleus during transcription of a strand of DNA, and carries the genetic code out of the nucleus into the cytoplasm
what is ribosomal RNA
is a large complex molecule made up of both double and single helixes. combines with proteins to form ribosomes. it is the site of translation of genetic code
what is the structure of transfer RNA
a small single stranded molecule that forms a clover leaf shape, with one end of the chain ending in an overhang at which point the amino acid it is carrying attaches itself. at the opposite end of the chain is a sequence of three bases called the anticodon
what is transfer RNA
A small single stranded molecule that transports amino acids to the ribosomes so proteins can be synthesized
what is the purpose of DNA
Makes up genes allowing for coding of proteins
what is the purpose of RNA
allows accurate copying of DNA
what are the four steps of genetic copying
-transcription
-splicing
-diffusion out of nucleus
-translation
what is an exon
a coding region
what is an intron
non-coding region
steps in transcription
- the dna in the nucleus is unwound
-weak hydrogen bonds between bases in DNA are broken causing the 2 strands to separate
-free RNA nucleotides in the nucleoplasm find their complimentary base pair on the DNA - the enzyme RNA polymerase then catalyses the formation of phosphodiester bonds between the ribose and phosphate group
-messenger RNA molecule is formed
-hydrogen bonds between bases of mRNA and DNA break
-mRNA leaves the nucleus - hydrogen bonds between the complementary base pairs of the 2 DNA strands reform, and DNA is wound back into a helix
where does transcription take place in eukaryotic cells
the nucleus
where’s does transcription take place in prokaryotic cells
the cytoplasm
what is translation
the process in which mRNA is read and translated into a protein
where does translation occur
at the ribosomes in the cytoplasm
what is the shape/ structure of tRNA
it is a single polynucleotide strand folded into a clover like structure with 3 branches, with hydrogen bonds between specific base pairs holding the molecule in this shape. it has a specific sequence of 3 bases at one end called the anticodon and an amino acid binding sit on the other end.
what are the steps in translation
- the mRNA attaches itself to a ribosome
- tRNA molecules carry amino acids to the mRNA
- a tRNA molecule with an anticodon that is complementary to the first codon on the mRNA attaches itself
- a second tRNA molecules attaches to the next codon
- the two adjacent amino acids join by a peptide bond, and the first tRNA molecule moves away
- then another tRNA comes along and attaches itself to the next codon on the mRNA, and its amino acid joins the second amino acid by a peptide bond
- the process continues producing a polypeptide chain until a stop codon is reached on the mRNA molecule
- the polypeptide chain then moves away from the ribosome
what is a homologous chromosome
a pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features
what is a chromatid
one of the two strands of a chromosome that are joined together by a single centromere prior to cell division
