Chapter 8 Flashcards
What is a gene?
a section of DNA that contains coded information for making a polypeptide and functional RNA
What is the name of the particular position that genes are found in?
Locus
Explain why scientists believe that at least 3 bases code for each amino acid
Only 20 amino acids occur regularly in proteins and each amino acid must have its own code of bases. As only 4 bases are present 3 must code for an amino acid otherwise there wouldnt be enough amino acids
What are 3 bases on DNA called?
a triplet
What are 3 bases on mRNA called?
a codon
What are 3 bases on tRNA called?
an anticodon
Why is DNA known as a degenerate code?
Because most amino acids are coded for by more than one triplet
Why is DNA known as non-overlapping?
Because each base is only read once - for its triplet
Why is DNA known as universal?
Because with a few minor exceptions each organism is made up of the same bases and is read in the same way
List 6 features of DNA
degenerate universal non overlapping always read one way contains stop codes the start of a DNA sequence is always the same triplet that is later removed if not needed
What are introns?
non coding sequences
What are exons ?
coding sequences
Homologous pairs come about because each organism comes about due to the joining or an ____ cell and a ____ cell. Each of these cells has ___ chromosomes consisting of 1 copy of each chromosome. So in the chromosome each each organism has one _____ chromosome and one ______ chromosome which carry the same _____ and have the same l_____ but may carry different ______
egg sperm 23 maternal paternal genes locus alleles
Define an allele
one of a number of alternative forms of a gene.
Define centromere
the region of a chromosome to which the microtubules of the spindle attach via the kinetochore during cell division
Define chromosome
a thread like structure made of proteins and DNA by which hereditary information is physically passed from one generation to the next
Define haploid number
a term referring to cells that contain only a single copy of each chromosome (number of chromosomes found in a gamete)
Define diploid number
a term referring to cells that contain 2 sets of each chromosome in the nucleus
Define meiosis
a type of nuclear division in which the number of chromosomes is halved
Define chromatid
one of 2 strands of a chromosome that are joined together by a single centromere prior to cell division
When are chromosomes visible?
when cells are dividing
Where a chromosomes when they are not visible?
dispersed throughout the nucleus
Each chromosome is made up of a long molecule of DNA and …
histones
What is the shape of:
DNA
mRNA
tRNA
double helix
single polynucleotide chain
single polynucleotide chain
What sugar does:
DNA contain
mRNA contain
tRNA contains
deoxyribose
ribose
ribose
Where are each of the following found?
DNA
mRNA
tRNA
nucleus
made in nucleus found throughout the cell
made in nucleus found throughout the cell
Define Genome:
the complete set of genes in a cell, including those in mitocondria and chloroplasts
define penteome
the range of proteins produced by the genome
What is the structure of RNA
a phosphate base, ribose sugar and adenine, gaunine, adenine and uracil bases
How many nucleotides is tRNA made of?
80
What is the shape of tRNA?
clover leaf shape
Each tRNA molecule is ___ to one ______ acid and has an _______ that is ________ to that amino acid
specific
amino
anticodon
specific
Histones associate in ___ to form structures called ___-
octamers
nucleosomes
Describe the basic process of protein synthesis:
DNA is split and the template strand is used to form a molecule of pre-mRNA that is made of complementary bases. The pre-mRNA molecule is spliced to remove introns and then the mRNA molecule acts as a template for translation as anticodons from the tRNA bind to the codons and attach the specific amino acid they carry to another amino acid to make a polypeptide chain
What is transcription?
The process of making pre-mRNA using a part of the DNA chain as a template
What enzyme moves along the strand to bind codons to triplets to make pre-mRNA?
RNA polymerase
What happens to make the pre-mRNA molecule detach from the DNA chain?
The RNA polymerase reaches a sequence of bases called a “stop code”
What is splicing?
The process of removing non coding introns from a chain of pre-mRNA to make mRNA that can code for proteins
Which out of prokaryotes and eukaryotes undergo splicing? Why
eukaryotes because they contain non coding introns which need to be removed in order for polypeptide synthesis to occur, whereas prokaryotes do not often contain introns and therefore do not need to remove them
What is translation?
The process of forming a polypeptide chain from a molecule of mRNA by using tRNA
Explain the basic process of translation
A ribosome binds to the starting codon of the mRNA and a tRNA molecule with a complementary anticodon binds to the codon. This tRNA molecule carries a specific amino acid. The next tRNA molecule with a complementary anticodon pair with the next codon carrying another amino acid. The 2 amino acids bond together forming a peptide bond. The ribosome moves down the chain to the next codon, linking the 2nd and 3rd amino acid. The 1st tRNA molecule is released and the process continues
Triplets determine _____, codons determine anticodons which determine amino acids which determines the _______ formed
codons
protein
