ch 9:chromosomes

Question 1

what is gene?

Answer 1

a specific length of DNA with specific sequence of nucleotides placed in specific position called locus & responsible for production of specific protein

Question 2

function of histone

Answer 2

DNA is very long thread, it reaches 1.8 meter in the nucleus of a cell. histones allows DNA to coil around them in a organized way to become compact to avoid formation of hopeless tangles

Question 3

role of mRNA

Answer 3

-translation to make a polypeptide chain
-mRNA carries copy of gene and travel across cytoplasm to small ribosomal subunit
-mRNA first codon is AUG it codes always for methionine
-two mRNA codons are exposed by large ribosomal subunit allowing two tRNA anticodons to bind to complementary mRNA codons by hydrogen bonds, putting amino acids in proper sequences
-mRNA allows ribosome to move one codon to allow next tRNA mol to enter

Question 4

role of tRNA

Answer 4

-each tRNA carries specific amino acid to ACC region
-two tRNA carry two amino acids into large ribosome subunit
-anticodon on tRNA binds to coon on mRNA, base pairing by H bonds
-tRNA molecules will then be released to be reused

Question 5

role of ribosomes

Answer 5

-translation to synthesize a polypeptide chain
-mRNA attaches to small ribosome subunit at specific binding site
-provides binding site for two tRNA molecules “P & A sites”
-brings two amino acids into large ribosome subunit held close together
-has peptidyl transferase enzyme to form peptide bond
-moves one codon on mRNA to allow next tRNA into assemble amino acids in sequence forming primary structure

Question 6

telomerase enzyme

Answer 6

-ensures that telomeres dont shorten each time DNA is replicated;
-synthesizes additional lengths of DNA (is used by DNA polymerase)
-telomeres have short length of RNA that acts as template for synthesis of DNA