4A - DNA, genes and protein synthesis

What's the genetic code of an organism?

The sequence of bases along its DNA

What does degenerate code mean?

Most amino acids are coded for by more than one triplet

What are the role of polypepetides?

To make up proteins from amino acids

What are genes?

A section of a sequence of bases within DNA

How many possible triplet codons are there?

64

How many amino acids can occur in proteins?

20

What does non-overlapping code mean?

Each base in the sequence is only read once

What does homologous chromosomes mean?

pairs of chromosomes that have the same genes at the same loci (locations) on the chromosome

What is a proteome?

The full range of proteins that can be expressed by a cell

What are histones?

proteins used in eukaryotic cells that DNA wraps around

What's a nucleotide?

The monomers of DNA/RNA made up of a phosphate group, pentose sugar and organic group

What's DNA helicase?

The enzyme which breaks hydrogen bonds that link base pairs in DNA

What's DNA polymerase?

The enzyme which joins nucleotides in a condensation reaction

What's the structure of a chromosome? (6 marks)

• each thread of chromosome is called a chromatid

• chromatid held together with centromere

• DNA in chromosomes is held together by his tone proteins

• Histones tightly coiled

• At the end of chromosomes there are telomeres

• contains a single molecule of DNA which has many genes along its length

What's a chromatid?

One of the two strands of a chromosome joined by a centromere

What's a centromere?

The point where two strands of the chromosome are attached to each other

What's a chromosome?

Thread-like structure of DNA that passes down information from generations

What's chromatin?

The material that makes up chromosomes (made of DNA and histones)

What's an intron?

All the parts of a gene that don't code for an amino acids

What's a homologous pair?

A pair of chromosomes (one paternal one maternaL)

What's are telomeres?

The ends of a chromosome

What are exons?

Bits of a gene that code for amino acids

What's a locus?

The position of a gene on a chromosome

What's a karyotype?

A profile of all the chromosomes in a cell

What's a gene?

Section of DNA on a chromosomes coding for one or more polypeptides

What's an allele?

One of the number of alternative forms of a gene

What molecule is longer? (P/E)

Eukaryotic cells

What shape does P DNA form?

A circle (No introns)

What shape does E DNA form?

Straight line (With introns)

Does P or E DNA coil?

Eukaryotic cells

Do P have non-coding DNA?

No

Do E have non-coding DNA?

Mitochondria and chloroplasts

What is a autosome?

Only non-sex chromosome

What is the function of DNA?

Codes genetic info

What is the function of mRNA?

Carries code from DNA in nucleus to site of protein synthesis

What is the function of tRNA?

Temporary carrier of amino acids

How many polynucleotide chains do mRNA and tRNA have?

1

What is the shape of mRNA?

single helix

What is the shape of tRNA?

clover leaf

What sugar do tRNA and mRNA contain?

Ribose

Where is DNA found?

Nucleus

Where is mRNA found?

nucleus and cytoplasm

Where is tRNA found?

cytoskeleton

What is the least stable RNA?

mRNA