DNA, genes and protein synthesis + genetic diversity

Teacher recommended

?
What is a gene?
A section of DNA that contains coded info for making polypeptides and functional RNA
1 of 99
What is the coded info in the gene in the form of?
A specific sequence of bases along the DNA molecule
2 of 99
What do polypeptides make up?
A protein.
3 of 99
Are enzymes proteins?
Yes
4 of 99
Where is a gene located?
The locus
5 of 99
The gene is a base sequence of DNA that codes for what 2 things?
1. The amino acid seqence for a polypeptide 2. functional RNA, tRNA and rRNA
6 of 99
Give some reasons as to why scientists suggested that there was a minimum of 3 bases that codes for each amino acid. (p1)
1. Only 20 different amino acids regularly occur in proteins 2. Each amino acid must have its own code of bases on the DNA 3.Only 4 different bases are present in DNA 4. If each base coded for a different amino acid, only 4 amino acids could be coded
7 of 99
Give some reasons as to why scientists suggested that there was a minimum of 3 bases that codes for each amino acid. (pt2)
5. Using a pair of bases, 16 different codes are possible which is still inadequate. 6. Three bases produce 64 different codes which is more than enough to satisfy the requirements of 20 amino acids
8 of 99
What are the features of the genetic code? (pt1)
1. A few aminoacids are coded for by only one single triplet. 2. The remaining amino acids are coded for by more than 1 triplet
9 of 99
What are the features of the genetic code? (pt2)
3. A triplet is always read in 1 particular direction along the DNA strand 4. The start of a DNA sequence that codes for a polypeptide is always the same triplet which codes for the amino acid methionine. If this amino acid does not form part of the
10 of 99
What are the features of the genetic code? (pt3)
polypeptide it is later removed.
11 of 99
What does it mean when saying the genetic code is universal?
Each triplet codes or the same amino acid in all organisms
12 of 99
What is indirect evidence fo evolution?
That the genetic code is universal
13 of 99
Why si the genetic code said to be degenerate?
It is degenerate because most amino acids are coded for by more than 1 triplet.
14 of 99
What are stop codons?
3 triplets do not code for any amino acid. These are stop codons. which mark the end of a polypeptide chain.
15 of 99
What does it mean when we say the genetic code is non-overlapping?
Non-overlapping - each base in the sequence is only read once
16 of 99
What are non-coding sequences within a gene called?
Introns
17 of 99
What are coding sequences within a gene called?
Exons
18 of 99
What differences within DNA are there with eukaryotic cells compared with prokaryotic cells?
Prokaryotic-DNA is shorter, form a circle, not associated w/ proteins so do not have chromosomes. Eukaryotic-longer, line, associate with proteins called histones to form chromosomes. DNA in mitochondria & chloroplasts looks like that in prokaryoti
19 of 99
When are chromosomes visible?
When the cell is dividing
20 of 99
When chromosomes first become visible what do they look like?
Appear as 2 threads, (chromatids) joined at a single point called a centromere.
21 of 99
Where is the DNA of chromosomes held?
In histones
22 of 99
How does DNA form a chromosome?
1. DNA molecule 2. DNA is combined with histones 3. DNA-histone complex is coiled 4. Coils fold to form loops 5. Loops coil and pack together to form the chromosome
23 of 99
What are homologous pairs?
2 Chromosomes that carry the same genes but not always the same alleles of the genes
24 of 99
What is a diploid? What is a haploid cell
Diploid cells contain the complete set of necessary chromosomes, while haploid have only half the number of chromosomes found in the nucleus.
25 of 99
What is the diploid number in humans?
46
26 of 99
What is an allele?
One of a number of alternative forms of a gene.
27 of 99
Each individual inherits one allele from each of its parents. When these are different is a different protein coded for?
Yes
28 of 99
Where does the synthesis of proteins occur?
In the cytoplasm
29 of 99
How is the coded info on the DNA in the nucleus transferred to the cytoplasm?
Sections of DNA code are transcribed onto a single-stranded RNA
30 of 99
What is mRNA?
The RNA that transfers the DNA code from the nucleus to the cytoplasm
31 of 99
What does the mRNA leave the nucleus via?
The nuclear pores
32 of 99
What is a codon?
A sequence of 3 bases on mRNA that codes for a single amino acid
33 of 99
What is a genome?
The complete set of genes in a cell
34 of 99
What is a proteome?
The full range of proteins produced by the genome.
35 of 99
Is RNA a polymer made up of mononucleotide sub-units?
Yes
36 of 99
Is RNA single or double-stranded?
Single
37 of 99
What is each nucleotide of RNA made up of?
Pentose sugar, organic base (A,U,C,G and a phosphate group
38 of 99
What are the 2 types of RNA that are important in protein synthesis?
1. Messenger 2. Transfer
39 of 99
Is mRNA relatively large or small?
It consists of thousands of mononucleotides and is a long, single strand
40 of 99
How is the base sequence of mRNA determined?
By the sequence of bases of DNA - This is transcription
41 of 99
What happens when the mRNA leaves the nucleus?
It associates with ribosomes where it acts as a template for protein synthesis
42 of 99
Is tRNA relatively small or large?
Small molecule as it is around 80 nucleotides. Single-stranded.
43 of 99
What is the shape of tRNA?
Clover leaf
44 of 99
Diagram of a tRNA molecule?
*
45 of 99
What is the basic process of polypeptide synthesis? (pt1)
1. DNA provides instructions in the form of a long sequence of bases 2. Complementary section of part of this sequence is made in the form of pre-mRNA - process=transcription 3. pre-mRNA is spliced to form mRNA 4. The mRNA is a template to which
46 of 99
What is the basic process of polypeptide synthesis? (pt2)
complementary tRNA molecules attach and the amino acids they carry are linked to form a polypeptide - process called translation
47 of 99
What is the transcription?
Making pre-mRNA using DNA as a template
48 of 99
What are the 5 steps to transcription? (pt1)
1. Enzyme acts on specific region of DNA causing the 2 strands to separate and expose nucleotide bases 2. Nucleotide bases on 1 strand (template strand) pair w/ complimentary nucleotides from the pool in the nucleus.
49 of 99
What are the 5 steps to transcription? (pt1)
3. Enzyme polymerase moves along the strand and joins nucleotides together to form pre-mRNA 4.As the enzyme adds the nucleotides, the DNA strand rejoin behind it 5. When the enzyme reaches the stop triplet it detaches and pre-mRNA production is done.
50 of 99
In prokaryotic cells, transcription results in direct production of mRNA. True or false?
True
51 of 99
When we say pre-mRNA is spliced in eukaryotic cells what does this mean?
Introns are removed to form mRNA
52 of 99
What would happen if intron were not removed?
They would prevent the synthesis of a polypeptide
53 of 99
In transcription, the triplet code of DNA is transcribed into a sequence of codons on mRNA. What is the next stage?
Translation
54 of 99
What is translation?
Where the codons on mRNA are translated into a sequence of amino acids that make up a polypeptide
55 of 99
There are about 60 different tRNAs. A particular tRNA has an anticodon. What is an anticodon?
a sequence of three nucleotides forming a unit of genetic code in a tRNA molecule, corresponding to a complementary codon in mRNA.
56 of 99
What is the process of translation (a.k.a how a polypeptide is made) (pt1)
1. A ribosome attaches to start codon on the mRNA 2. tRNA molecule w/ complementary anticodon sequence moves to ribosome and pairs up w/ codon on mRNA. tRNA carries a specific amino acid 3. Step 2 continues
57 of 99
What is the process of translation (a.k.a how a polypeptide is made) (pt2)
4. The ribosome moves along mRNA, bringing 2 tRNA together at any 1 time pairing w/ the codons on the mRNA 5. 2 Amino acids on tRNA are joined by a peptide bond using enzyme+ATP 6. Ribosome continues to move along, linking the amino acids
58 of 99
What is the process of translation (a.k.a how a polypeptide is made) (pt3)
7. As the amino acids link they separate from their tRNA and tRNA is free to collect another amino acid from amino acid pool in cell 8. Polypeptide chain is built 9. Synthesis carries on till the ribosome reaches a stop codon
59 of 99
How is a protien assembled?
1. Polypeptide is coiled or folded, producing secondary structure 2. Secondary structure is folded, producing tertiary structure. 3. Different polypeptide chains are linked to form quaternary structure
60 of 99
What is mutattion?
Any change to the quantity or the base sequence of DNA of an organism.
61 of 99
When do mutations occur that cause them to be inherited?
Mutations may occur during the formation of gametes may be inherited
62 of 99
What is gene mutation?
Any change to one or more nucleotide bases or change in sequence of bases
63 of 99
What are the 2 types of gene mutation?
Substitution of bases and deletion of bases
64 of 99
What are chromosome mutations?
Changes in the structure of a chromosome
65 of 99
What are the 2 forms that chromosome mutation can take?
1. Changes in whole sets of chromosomes 2. Changes in number of individual chromosomes
66 of 99
When does changes in whole sets of chromosomes occur?
When organisms have 3 or more sets of chromosomes rather than the usual 2. (polyploidy)
67 of 99
Why are there changes in the number of individual chromosomes sometimes?
Sometimes individual homologous pairs of chromosomes fail to separate during meiosis - nondisjunction
68 of 99
What does non-disjunction cause?
Results in a gamete having one more or one fewer chromosomes
69 of 99
What is an example of a disease caused by nondisjunction?
Down syndrome -chromosome 21
70 of 99
What are the 2 ways that cell division occurs?
1. Mitosis - produces 2 daughter cells w/ the same number of chromosomes as the parent cell and as each other 2. Meiosis - produces 4 daughter cells, each w/ half the number of chromosomes as parent cell
71 of 99
What is the importance of meiosis?
In sexual reproduction 2 gametes fuse to give rise to new offspring, if each gamete were diploid this would cause the offspring to have too many chromosomes so it halves during meiosis.
72 of 99
Every diploid cell contains two sets of what and where do they come from?
2 sets of chromosomes and they come from the parents
73 of 99
What happens during meiosis to the homologous pairs of chromosomes?
They separate so only one chromosome from each parent cell enters the daughter cell - haploid number
74 of 99
Meiosis involves two nuclear divisions , what are they? (pt1)
Meiosis 1-homologous chromosomes pair up & their chromatids wrap around each other. Equivalent portions of chromatids may cross over. By the end of the division homologous pairs separated, w/ 1 chromosome from each parent cell going into a daughter
75 of 99
Meiosis involves two nuclear divisions , what are they? (pt1)
Meiosis 2 - chromatids move apart. At the end 4 cells have been formed, each containing 23 chromosomes in humans
76 of 99
How does genetic variation bring out genetic variation?
1. Independent segregation of homologous chromosomes 2. New combinations of maternal and paternal alleles by crossing over
77 of 99
What is a gene?
A length of DNA that codes for a polypeptide
78 of 99
What is locus?
The point of a gene on a chromosome or DNA molecule
79 of 99
What is an allele?
One of the different forms of a particular gene
80 of 99
What are homologous chromosomes?
A pair of chromosomes,one maternal and one paternal that have the same gene loci
81 of 99
What is independent segregation of homologous chromosomes?
During meiosis 1, each chromosomes lines up alongside its homologous partner, when the pairs arrange themselves they do this at random. One of each pair will pass to each, which one depends on how they are lined up and how they are lined up is random
82 of 99
What is genetic recombination by crossing over?
1. Chromatids of each pair become twisted around each other 2. Tensions are created & portions of chromatids break off 3. Broken portion rejoin with chromatids of its homologous partner
83 of 99
All members of the same species have the same genes. True or false?
True
84 of 99
How is genetic diversity achieved if members of the same species have the same genes?
The different combination of the 2 alleles of the gene
85 of 99
What is genetic diversity?
The total number of different alleles in a population
86 of 99
What is a population?
is a group of individuals of the same species that live in the same place and can interbreed
87 of 99
Can a species consist of different populations?
Yes
88 of 99
The greater the number of different alleles, the greater the what?
Genetic diversity within a species
89 of 99
How is genetic diversity reduced?
When a species has fewer different alleles
90 of 99
How does greater genetic diversity help a species to survive?
When conditions of the environment change the species w/ more different alleles is likely to survive bc there is a higher chance for one organism to have the allele that allows a characteristic that helps the organism to survive + breeds + pass down
91 of 99
Differences between reproductive success of individuals affects allele frequency in populations. How does this process work?
1.gene pool, variety of alleles 2.random mutation of alleles within gene pool result in new allele of gene 3.allele gives advantage 4.better adapted to survive 5.better chance at breeding 6.pass alleles onto next generation
92 of 99
Differences between reproductive success of individuals affects allele frequency in populations. How does this process work? (pt2)
7. Frequency of advantageous allele is more than the non advantageous alleles
93 of 99
What is selection?
The process by which organisms that are better adapted to their environment tend to survive and breed
94 of 99
What are the 2 types of selection?
Directional and stabilising
95 of 99
What is directional selection?
Selection favours individuals tat vary in one direction from the mean of the population and it changes the characteristics of a population
96 of 99
What is stabilising selection?
Selection favours average individuals and preserves the characteristics of a population
97 of 99
What is an example of directional selection?
Penicillin
98 of 99
What is an example of stabilising selection?
Human birth rates
99 of 99

Other cards in this set

Card 2

Front

What is the coded info in the gene in the form of?

Back

A specific sequence of bases along the DNA molecule

Card 3

Front

What do polypeptides make up?

Back

Preview of the front of card 3

Card 4

Front

Are enzymes proteins?

Back

Preview of the front of card 4

Card 5

Front

Where is a gene located?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

DNA
See all Biology resources »See all DNA, genetics and evolution resources »