Genetics Flashcards
Describe eukaryotic DNA
Large/long
Associated with histones
Found in linear chromosomes
Contained within the nucleus
Describe prokaryotic DNA
Shorter/single stranded
Not associated with histones
Single, circular loop
Free-floating in the cytoplasm
What is the genetic code?
Triplet code
Non-overlapping
Universal
What does it mean that the genetic code is a triplet code?
Every 3 bases forms a codon and one codon = one amino acid
What does it mean that the genetic code is non-overlapping?
It reads a sequence and separates it into 3s
123456 = 123, 456, 789 not 123, 234, 456
What does it mean that the genetic code is universal?
Each triplet code always codes for the dame amino acid
How many possible triplets is there?
64
How many different amino acids is there?
20
What does it mean that the code s.is degenerate?
Some amino acids are coded by more than one base
Do all triplet codes result in an amino acid?
No some act as start and stop codons
Describe the process of transcription
DNA helicase breaks H bonds
Free floating RNA nucleotides find complementary base pairs
RNA polymerase forms phosphodiester bonds between each mRNA nucleotide to form pre-mRNA
What is removed in splicing?
Introns
What are exons joined to form?
mRNA
What must be removed before mRNA leaves the nucleus?
Non-coding pieces of mRNA (introns)
What is translation?
The process by which mRNA is used to make a specific polypeptide
Describe the process of translation
mRNA moves out of the nucleus via nuclear pores
mRNA attaches to ribosome
Anti-codon forms temp H bonds with complementary bases on mRNA
Peptide bond forms between amino acids
When does the process of translation stop?
When a stop codon is reached
What will the other ribosomes that pass along the mRNA produce?
An identical polypeptide
What does tRNA do?
Transport specific amino acids
How many different types of tRNA is there?
20
What do all the different tRNA have in common?
The same structure
What is the structure of tRNA?
Bases folded to form a clover structure Attachment site for amino acids Anti-codon Base pairing Consists of a single polynucleotide strand of RNA
What is a mutation?
Any change in one or more nucleotide base or a change in the sequence of bases in DNA
What are mutations?
Random
Spontaneous
Natural
What are the three types of mutations?
Deletion
Insertion
Substitution
What is deletion?
A nucleotide is lost from the sequence
What is insertion?
A nucleotide is added to the sequence
What is substitution?
A nucleotide is replaced by another nucleotide with a different base
Which mutation will have the biggest impact and why?
Deletion and insertion as it will cause a frame shift (all amino acids effected)
Why will substitution have minimum impact?
As it will only effect one amino acid or non if it is degenerate
What are the two types of chromosomal mutation?
Polyploidy
Non-disjunction
What is polyploidy?
When organisms have three or more sets of chromosomes
What is non-disjunction?
When chromosomes fail to separate during meiosis
Which organism does polyploidy mostly occur in?
Plants
What is the role of mitosis meiosis in the animal body?
Growth and repair - MI
Production of gametes - ME
How many cell divisions is there in mitosis and meiosis?
1 - MI
2 - ME
How many daughter cells are produced in mitosis and meiosis?
2 - MI
4 - ME
What is the genetic composition of the daughter cells in mitosis and meiosis?
Diploid - MI
Haploid - ME
What is the similarity of the daughter cells to the parent cells in mitosis and meiosis?
Identical - MI
Similar but not identical - ME
What is meiosis?
The process by which a diploid nucleus divides to produce four haploid nuclei
What are the two forms of genetic variation during meiosis?
Crossing over (exchange of alleles) Independent segregation (Random arrangement of homologous chromosomes)
Describe meiosis
DNA unravels and replicates so there are two copies of each (chromatids)
DNA condenses to form double armed chromosomes formed by two sister chromatids
Joined by a centromere
Meiosis 1- chromosomes arrange themselves into homologous pairs
These are separated + halved
Meiosis 2- Sister chromatids are separated + centromere divided
4 genetically different haploid cells produced
What is genetic diversity?
The total number of different alleles in a population
What does it mean if there is greater genetic diversity in a population?
More likely organisms are going to be suited to their environment
What is phenotype?
Observable physical characteristics an organism has
What is genotype?
Genetic makeup of an organism
What is the gene pool?
The total number of alleles in a population at a specific time
What is allele frequency?
The number of times an allele occurs within the gene pool
What is a normal distribution curve look like?
Data surrounds a central point
Curve is symmetrical
Curve is bell shaped
What are most characteristics a result of?
Multiple genes (polygenes)
What are polygenes effected by?
The environment
If the environment changes what part of the distribution curve changes?
The mean