DNA, genes and chromosomes Flashcards
what is a gene?
a base sequence of DNA that codes for:
-the amino acid sequence of a polypeptide
-a functional RNA (including ribosomal RNA and tRNAs)
what does a gene occupy?
a fixed position, called a locus, on a particular DNA molecule
what is a triplet and what does it do?
a sequence of three DNA bases that codes for a specific amino acid
what three terms describe the genetic code?
universal, non-overlapping and degenerate
what is meant by the code being degenerate?
most amino acids are coded for by more than one triplet
what are stop codons?
three triplets that do not code for any amino acids, and mark the end of the polypeptide chain
what is meant by the code being non-overlapping?
each base in the sequence is only read once
what is meant by the code being universal?
each triplet codes for the same amino acid in all organisms, with a few minor exceptions
this is indirect evidence for evolution
in eukaryotes, what does much of the nuclear DNA do?
doesn’t code for polypeptides
between genes there are non-coding sequences made up of multiple repeats of base sequences
what are exons?
certain sequences within genes that code for amino acid sequences
what are introns?
non-coding sequences that separate exons
what is the genome?
the complete set of genes in a cell
what is the proteome?
the full range of proteins that a cell is able to produce
what is the Central Dogma?
states that information flows in one direction. DNA to RNA to Protein
this is common to all organisms
how is DNA in prokaryotic cells?
short, circular and not associated with proteins (histones)
therefore prokaryotic cells do not have chromosomes
how is DNA in eukaryotic cells?
longer, linear and associated with proteins called histones
what is a chromosome?
Thread like structures made of protein and DNA which carry genetic information
what is a chromatid?
One strand of a replicated chromosome.
what is chromatin?
a mixture of DNA and proteins that form the chromosomes found in the cells of humans and other higher organisms.
what two things are chromosomes made of?
two SISTER chromatids as a result of DNA replication
what is a sister chromatid?
one of two identical copies that makes up a chromosome.
it is a long strand of DNA with identical alleles of a gene in the same loci as the chromatid it is a copy of
what is an allele?
an alternative form of a gene
what is a loci/locus?
position of a gene on a chromosome/ DNA molecule
what are homologous chromosomes?
a pair of matching chromosomes, with the same genes in the same loci but each chromosome may have a different allele of the gene.
one chromosome is paternal and its homologous pair is maternal
what is meant by a chromosome being maternal or paternal?
paternal- inherited from father
maternal- inherited from mother
