Section 4 - DNA, genes and protein synthesis Flashcards
What can reduce species diversity in agriculture?
Monocultures
Overgrazing
Draining wetlands
How can we compare genetic diversity between species?
DNA sequences Observable characteristics Amino acid sequences
During transcription, what is reading the open DNA to make a sequence of complementary bases?
RNA polymerase
How do you write the scientific names of species?
Underlined Italics First letter of first name uppercase
Write the taxonomic ranks in order
Domain Kingdom Phylum Class Order Family Genus Species
What is artifical classification?
single or at most only a few characteristics to group plants
Which bases pair with 3 hydrogen bonds?
G to C
Where else can DNA be found in eukaryotic cells?
Mitochondria Chloroplasts
What type of bond is formed between the amino acids during translation?
Peptide
Why is splicing needed during transcription?
To remove introns
Which bases pair with 2 hydrogen bonds?
A to T
What is a triplet on a mRNA molecule referred as?
codon
What are some facts about mRNA?
Short lifetime Single stranded Present in transcription Present in translation
What is different from pre-mRNA and mRNA?
Introns are removed
What type of classification groups organisms based on evolutionary relationships?
Phylogenetic classification
Define the term allele.
The different characteristics coded for by the same gene
How do we name species?
Binomial system
What is a triplet on a tRNA molecule referred as?
Anticodon
Define the term gene.
A section of DNA at a specific position
What classifies organisms into the domain bacteria?
70S ribosomes Cell walls contain murein No histones associated with DNA
How could you describe other types of eukaryotic DNA? (not found in the nucleus) *
Short Not associated with proteins
What are the 3 domains?
Eukarya Bacteria Archaea
What is the role of rRNA?
Makes up ribosomes
What is the protein associated with DNA?
Histone
What do polypeptides make up?
Proteins
What do enzymes do?
Control chemical reactions they are responsible for an organisms development and activities.
What is a locus?
A gene located at the particular position on the DNA molecule.
What does DNA code for?
- Amino acid sequence of polypeptide - Functional RNA, including ribosomal RNA and transfer RNAs
How many bases code for each amino acid?
3
How many naturally occurring amino acids are there?
20
What are the four different bases in DNA?
Adenine, guanine, cytosine and thymine.
How many different codes are produced with three bases?
64 this satisfies the requirement for 20 amino acids
Explain the features of genetic code
Few amino acids are coded for by only a single triplet. The remaining AA are coded for by 2-6 triplets each known as degenerate code Start - codes for polypeptide and always the same triplet. Stop codes mark the end. Codes are non-overlapping. Code is universal
What is degenerate code?
Most amino acids are coded for by more than one triplet
What are the coded for the start of a DNA sequence?
Codes for a polypeptide with amino acid methinonine
Why does DNA provide indirect evidence for evolution?
The code is universal with few minor exceptions as each triplet codes for the same amino acid in all organisms.
What are exons?
Genes that code for amino acids.
What are introns?
Non-coding genes for DNA.
What are the two types of cells?
Prokaryotic and eukaryotic cells.
What are the genetic differences between Pro and Eukaryotic cells?
Pro - DNA is shorter, in a circle and not associated with protein molecules. No chromosomes. Eu- Longer molecules, line in association with proteins called histones forming chromosomes
What do histones do?
In eukaryotic cells that form chromosomes.
The DNA in chromosomes are held together by histones.
What is the DNA like inside the prokaryotic cells?
Short, circular and not associated with proteins.
What is a chromatid?
One of two threads of a chromosome.
In an average human cell, what is the length of DNA?
Around 2m
where do humans get their two types of chromosomes?
One complete set from the egg - maternal chromosomes.
One complete set from the sperm - paternal chromosomes.
These are homologous pairs and the total number is referred to as the diploid number.
What is the diploid number in humans/
46 chromosomes.
23 sets
What is a homologous pair?
Always two chromosomes that carry the same genes but not necessarily the same alleles of the genes.
What is an allele?
One of a number of alternative forms of a gene.
What is a gene?
Genes are sections of DNA that contain coded information in the form of specific sequences of bases.
Each gene exists in two, occasionally more, different forms.
Each of these forms is called an allele.
What is a mutation?
Any changes in the base sequence of a gene produces a new allele of the gene and results in a different sequence of amino acids being coded for.
What can a mutation lead to?
The production of a different polypeptide, and hence a different protein.
Sometimes this different protein may not function properly or may not function at all.
When the protein produced is an enzyme it may have a different shape.
The new shape may not fit the enzymes substrate.
As a result, the enzyme may not function and this can have serious consequences for the organism.
how many different types of tRNA are there?
60 different.
A particular tRNA has a specific anticodon and attaches to a specific amino acid.
Each amino acid, therefore, has one or more tRNA molecules, with its own anticodon of bases.
What does mRNA do ones it has passed out of the nuclear pores?
determines the synthesis of a polypeptide.
How are polypeptides made?
- Ribosome becomes attaches to start codon at one end of the mRNA molecule
- tRNA molecule with complementary anticodon sequence moves to the ribosome and pairs with a codon on the mRNA. tRNA carries specific amino acid.
- tRNA molecule with complementary anticodon pairs with the next codon on the mRNA.
- The two amino acids in tRNA are joined by a peptide bond using an enzyme and ATP which is hydrolysed to provide the required energy.
- The ribosome moves to the third codon linking the amino acids.
- As this happens the first tRNA is released from its amino acid and is free to collect another amino acid from the pool in the cells
- The process continues up to 15 amino acids per second until the chain is built up.
- Continue until reaching the stop codon.
In what stage of protein synthesis is linked with a number of polypeptide chains joining?
quarternary structure
What normally happens to the polypeptide after translation?
- polypeptide is coiled or folded producing its secondary structure
- the secondary structure is folded producing tertiary structure
- different polypeptide chains along with an non-protein groups are linked to form the quaternary structure.
