DNA and chromosomes Flashcards
what is a gene?
a base sequence of DNA that codes for the amino acid sequence of a functional RNA molecule (or a polypeptide)
what is an allele?
one of multiple versions of DNA sequence at a given genomic location.
what is a homologous chromosome?
two chromosomes that determine the same genetic characteristics.
what is meant by a locus?
the specific position of a gene on a chromosome.
what is the telomere?
the region of repetitive nucleotide sequences at each end of a chromosome - protects it from deterioration or fusion with neighbouring chromosomes.
what are chromatids?
one of the identical halves of a chromosome that has been replicated in preparation for cell division.
what is a histone?
a protein that DNA wraps around tightly to form a chromosome.
how is DNA in eukaryotic cells different from DNA in prokaryotic cells?
eukaryotic - found in nucleus, long and linear, associated with histone proteins to form chromosomes, contains non-coding DNA.
prokaryotic - short and circular, not associated with proteins, does not contain non-coding DNA.
what is transcription?
the process of making pre-mRNA from DNA.
what does RNA polymerase do?
it binds to DNA and separates the DNA strands to form into a complementary strand of RNA by using one DNA strand as a template to assemble the nucleotides.
what does a histone provide for a chromosome?
it provides structural support to the chromosome.
state two similarities between the DNA in eukaryotic and prokaryotic cells.
- nucleotides are joined by phosphodiester bonds to form a DNA polymer chain.
- both nucleotide monomers are made up of a phosphate group, deoxyribose sugar and a nitrogenous base.
state the two organelles found in eukaryotic cells that have prokaryotic DNA - describe the DNA.
- mitochondria and chloroplasts
- DNA is short, circular and not associated with a protein.
give two examples of functional RNA.
rRNA and tRNA
what are codons?
codons are three bases on mRNA that code for one specific amino acid.
describe mRNA.
- found in the cytoplasm and nucleus
- made by transcription by being copied from DNA (so mRNA is complementary to DNA sequence)
how does mRNA differ from DNA?
- single stranded, not double
- contains ribose, not deoxyribose
- contains uracil instead of thymine
describe tRNA.
- in the cytoplasm, amino acids attach to tRNA.
- each tRNA molecule is specific for one amino acid.
- its involved in translation, in which it carried the amino acids needed to make proteins for ribosomes.
