4) Genetic Information, Variation, and Relationships Between Organisms Flashcards
- DNA, genes, and protein synthesis - Genetic Diversity - Biodiversity
in terms of their purpose, what is the difference between RNA and DNA?
DNA holds genetic information, whereas RNA transfers genetic information from DNA to ribosomes
what are ribosomes made of?
rRNA and proteins
what are the components of DNA nucleotide?
deoxyribose
a phosphate group
an organic base
which bases are purine bases? why?
adenine and guanine
they have double ring structures
what are the components of an RNA nucleotide?
ribose
a phosphate group
an organic base
which organic bases are pyrimidines? why?
thymine, uracil, and cytosine
they have single ring structure
which of the bases can a DNA nucleotide have?
adenine, thymine, cytosine, guanine
which of the bases can an RNA nucleotide have?
adenine, uracil, cytosine, guanine
how are nucleotides joined? give the bond and reaction
by phosphodiester bonds formed in condensation reactions
what bonds join complementary bases?
hydrogen bonds
what is the genetic code?
the order of bases on DNA, which consists of triplets of bases
what is a codon?
a sequence of 3 bases on mRNA that codes for a specific amino acid
what is a gene?
a length of DNA on a chromosome that codes for a sequence of amino acids in a polypeptide chain
what is a locus?
the location of a gene on a chromosome
what are introns and exons?
- introns are non-coding sections of DNA
- exons are coding sections
how many different amino acids are there?
20
how many possible triplets are there?
64
what does non-overlapping mean?
each base in a sequence is read once and is only part of one triplet
what does degenerate mean, in relation to the genetic code?
more than one triplet codes for the same amino acid
what is the advantage of the genetic code being degenerate?
reduces the number of mutations
what are the differences between eukaryotic DNA and prokaryotic DNA?
EUKARYOTIC
- long and linear
- associated with histones
PROKARYOTIC
- short and circular
- not associated with proteins
how many chromosomes are there in each human body cell?
46
how are chromosomes arranged in each cell?
in homologous pairs
what is a homologous pair?
two chromosomes that carry the same genes at the same locus
why are the chromosomes in a homologous pair not identical?
because they can carry different alleles of the same gene
which chromosome determines sex?
23
what is an allele?
an alternative version of the same gene
what are the two stages of protein synthesis?
transcription and translation
what is transcription?
the formation of pre-mRNA in eukaryotes and mRNA in prokaryotes from a section of the template strand of DNA
where does transcription occur?
in the nucleus
during what process is mRNA made?
transcription
what is the role of mRNA?
carries the genetic code from the DNA to the ribosomes, where it’s used to make a protein
describe the structure of mRNA
single polynucleotide strand
what are groups of 3 adjacent bases called in mRNA?
codons
what process is tRNA involved in?
translation
what is the role of tRNA?
carries the amino acids, used to make proteins, to the ribosomes
describe the structure of tRNA
single polynucleotide strand folded into a clover shape
what bonds hold tRNA into its clover shape?
hydrogen bonds between specific base pairs
what do tRNA molecules have at each end?
an anticodon and an amino acid binding site
what is an anticodon?
a sequence of 3 nucleotide bases at one end of a tRNA molecule that is specific to an mRNA codon
where does transcription take place in eukaryotic and prokaryotic cells?
- eukaryotic = in the nucleus
- prokaryotic = in the cytoplasm
where does translation occur?
at the ribosomes in the cytoplasm
describe the process of translation
- mRNA attaches to a ribosome and tRNA collects amino acids from cytoplasm and carries them to the ribosome
- tRNA attaches to mRNA by complementary base pairing, two molecules of tRNA attach at a time
- amino acids attached to two tRNA molecules join by a peptide bond and tRNA molecules detach from the amino acids to leave them behind
- process repeats leading to the formation of a polypeptide chain until a stop codon is reached
what is a genetic mutation?
any change in the base sequence or quantity of DNA
what can a change in the base sequence of a gene result in?
a change to the sequence of amino acids
why does a genetic mutation not always lead to a change in the amino acid sequence?
because the genetic code is degenerate (more than one triplet codes for the same amino acid)
what are the types of genetic mutation?
- substitution
- deletion
- addition
- inversion
- duplication
- translocation
what are the two kinds of mutations that can occur in chromosomes?
polyploidy and non-disjunction
what is polyploidy?
changes that occur in the whole set of chromosomes so that an individual has three or more sets of chromosomes instead of two
what is non-disjunction?
when chromosomes fail to separate correctly in meiosis, resulting in the gametes and therefore any zygotes formed having one more or fewer chromosome than they should
how many daughter cells are produced by meiosis?
4
are daughter cells produced by meiosis genetically identical or unique?
genetically unique
how many chromosomes do gametes have in relation to the parent cell?
half the number
what is the role of meiosis?
production of haploid gametes
why must gametes be haploid?
so that when two gametes fuse, the zygote produced is diploid
by what two ways is genetic variation achieved?
- independent segregation
- crossing over
when does independent segregation occur?
during meiosis 1
Describe the process of meiosis
1) DNA unravels and replicates so there are 2 copies of each chromosome
2) DNA condenses to form double-armed chromosomes each made from a sister chromatids
3) meiosis 1 - chromosomes arrange themselves into homologous pairs
4) Homologous pairs are separated, halving the chromosome number
5) meiosis 2 - each pair of sister chromatids, that make up each chromosome, are separated
6) 4 genetically different (from each other) haploid daughter cells are produced
