Reproduction, the genome and gene expression Flashcards
what are the advantages of sexual reproduction? (3)
-produces variation in the off springs
-survival advantage: species can adapt to new environments due to variation
-a disease is less likely to affect all population
what are the disadvantages of sexual reproduction? (2)
-time and energy needed to find a mate
-not possible for isolated individual (e.g species on the brink of extinction)
advantages of asexual reproduction: (3)
-population can increase rapidly if the (environmental) conditions are favourable
-only one parent is needed so it’s more time and energy efficient than sexual rep
-faster than sexual reproduction
disadvantages of asexual reproduction: (3)
-no variation in population
-specie may be suited to only one habitat
-disease may affect entire population
what does meiosis produce? and what does this result in?
four daughter cells, each with half the number of chromosomes
genetically different haploid gametes
what does meiosis produce in animals and plants?
sperms and egg cells in animals and pollen in plants
what is the genetic material in the nucleus of a cell made up of?
DNA
what is DNA made up of?
a polymer made up of nucleotides
what are nucleotides made up of?
a sugar and a phosphate group, with one of four different bases, A, C, T or G, attached
how is the double-helix structure of DNA formed?
and what holds this double-helix structure?
The nucleotides join together, forming two strands.
-weak hydrogen bonding between complementary base pairs
what are the complementary base pairs?
thymine pairs with adenine (T–A)
guanine pairs with cytosine (G–C).
Describe the structure of DNA:
-a polymer made up of two strands coiled to form a double helix
-strands are linked by a series of complementary base pairs joined together by weak hydrogen bonds
-nucleotides that consist of a sugar and phosphate group with one of the four different bases attached to the sugar
what are chromosomes?
long strands of DNA, made up of genes
what is a gene?
a small section of DNA in a chromosome
what does a gene do?
Each gene codes for a particular sequence of amino acids in order to make a specific protein
what is a genome?
the entire DNA of an organism
how is the HGP helpful in medicine?
-mapping of a person’s genome can help in predicting how likely they are to develop certain conditions
Method for extracting DNA from a kiwi: (5)
1- Peel the skin from half a kiwi fruit and mash it up
2- Mix a teaspoon of salt and small volume of washing up liquid into the fruit
3- Gently heat this mixture at about 60°C for five minutes
4- Filter the mixture and retain only the filtrate (the filtered liquid)
5- Cool using an ice bath and gently pour chilled ethanol onto the top of the filtrate
what will you observe from the fruit DNA extraction ?
strands of DNA with bubbles in them at the boundary between the filtrate and the chilled ethanol.
what are the four bases?
thymine, T
adenine, A
guanine, G
cytosine, C
what does the sequence of bases in the gene control?
which amino acids are joined in order to make a specific new protein (or enzyme) molecule
what happens to amino acids after they have joined together?
due to this, how could you define a protein?
they are folded into their correct shape to make them functional.
A protein is a chain of amino acids, folded into the correct shape.
what is a triplet?
what is its purpose?
three bases.
A triplet of DNA bases codes for one amino acid.
describe the process of genes coding for proteins: (3)
1- Each triplet of bases codes for one particular amino acid.
2- Amino acids are made in the number and order dictated by the number and order of base triplets.
3- The amino acid molecules join together in a long chain to make a protein molecule. The number and sequence of amino acids determines which protein is produced.
what needs to happen in order for a gene to be expressed?
where does this process take place?
the base sequence of DNA is copied or transcribed into mRNA
the nucleus
what must happen to the strands of DNA before the transcription process?
how does this occur?
The two strands of the DNA helix are unzipped
by breaking of the weak Hydrogen bonds between base pairs.
what causes the unwinding of the two DNA strands?
This unwinding of the helix is caused by an enzyme (helicase enzyme).
what does a single codon code for?
a single amino acid
describe the process of transcription into the mRNA: (4)
1- The two strands of the DNA helix are unzipped by breaking of the weak Hydrogen bonds between base pairs. This unwinding of the helix is caused by an enzyme (helicase enzyme).
2- The enzyme RNA polymerase attaches to the DNA in a non-coding region just before the gene.
3- RNA polymerase moves along the DNA strand. Free RNA nucleotides form hydrogen bonds with the exposed DNA strand nucleotides by complementary base pairing to form a strand of mRNA
4- The newly formed strand of mRNA is now ready to leave the nucleus and travel to the ribosome.
what is the difference between the bases of DNA and RNA?
RNA nucleotides contain the same bases as DNA, except that T is replaced by U. U base pairs with A.
what is the relationship between the the strand of mRNA and the DNA?
-what is this called?
the mRNA will be an exact opposite copy of the DNA strand
a complementary copy
