topic 4: gene expression Flashcards
what is genotype and phenotype?
genotype: the DNA sequence of an organism
phenotype: the observable physical characteristics
what is the central dogma of genetic information flow?
DNA (transcription) —> RNA (translation) —> protein
what is phenotype the result of?
protein production or gene expression
what is gene expression? how many stages does it include?
- it is DNA-directed protein synthesis
- includes 2 stages:
(1) transcription
(2) translation
what molecule acts as an intermediate between genes (genotype) and the proteins which they code for (phenotype)?
RNA
what is transcription?
- the DNA-directed synthesis of RNA
- transcription produces messenger RNA (mRNA)
what is translation?
- the synthesis of a polypeptide which occurs under the direction of mRNA
- translation occurs on ribosomes
what are the differences in gene expression between prokaryotes and eukaryotes?
prokaryotes:
- no nuclear envelope to separate transcription and translation: both take place in the cytoplasm
- mRNA produced by transcription is immediately translated without further processing (no RNA processing)
- translation can start before the end of transcription
eukaryotes:
- the nuclear envelope separates transcription from translation
- transcription: takes place in the nucleus
- RNA processing: (takes place in the nucleus) eukaryotic DNA transcripts are modified to yield the mRNA (final product of transcription)
- translation: takes place in the nucleus
what is pre-mRNA?
also known as primary transcript, is the initial RNA transcript
[only present in eukaryotes]
information flow from gene to protein is based on?
- a triplet code consisting of 3 consecutive nucleotides known as codon
- each gene is transcribed in a complementary mRNA containing the nucleotide triplets (codons)
- each codon specifies the addition of a specific amino acid
- the gene is translated into an amino acid chain forming a polypeptide chain
which DNA strand of the 2 is used as a template for the synthesis of the complementary RNA strand?
the 3’ to 5’ DNA strand (known as the template strand)
in what direction is RNA synthesized?
RNA polymerase synthesizes RNA in a 5’ - 3’ direction using the template DNA strand
in what direction are codons on the mRNA read during translation?
they are read in the 5’ - 3’ direction by the ribosomes
if you’re given the double stranded DNA figure unlabeled, which strand is used as a template for the mRNA strand synthesis?
the 3’ - 5’ strand
why is the DNA coding strand named so?
it is called the coding strand because it has the exact same sequence as the mRNA strand produced (with T replaced with U)
mRNA IS ALWAYS PRODUCED IN THE _______ DIRECTION
5’ - 3’
how many codons are there?
- 64 codons
- 61 code for amino acids
- 3 are “stop” signals to end translation
what is the start codon?
AUG (methionine)
what are the characteristics of the genetic code?
- it is redundant: more than 1 codon can encode for a specific amino acid
- it is not ambiguous: each codon can specify only 1 amino acid
list the names of the 20 amino acids
1. ala
2. arg
3. asn
4. asp
5. cys
6. gln
7. glu
8. gly
9. his
10. ile
11. leu
12. lys
13. met
14. phe
15. pro
16. ser
17. thr
18. trp
19. tyr
20. val
- alanine
- arginine
- asparagine
- aspartic acid
- cysteine
- glutamine
- glutamic acid
- glycine
- histidine
- isoleucine
- leucine
- lysine
- methionine
- phenylalanine
- proline
- serine
- threonine
- tryptophan
- tyrosine
- valine
give an example to how genes can be transcribed and translated after being transplanted from one species to another
- genetically modified bacteria
- bacteria can be programmed by the insertion of human genes to produce certain human proteins for medical use
- example: INSULIN
what do ribonucleotides (RNA nucleotides) consist of?
- a nitrogenous base (A, G, C, U)
- a pentose sugar (ribose)
- a phosphate
what are the differences between DNA and RNA?
- DNA is double-stranded, RNA is single-stranded
- the sugar in DNA is deoxyribose, the sugar is RNA is ribose
- the base URACIL is present in RNA to replace thymine
what are the major types of RNA and their functions?
- mRNA (messenger): is translated into proteins
- rRNA (ribosomal): part of ribosome structure
- tRNA (transfer): transfers amino acids to the growing polypeptide chain during translation