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biology > variation and selection > Flashcards

variation and selection Flashcards

1
Q

what does DNA stand for

A

deoxyribonucleic acid

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2
Q

where is DNA found

A

the nucleus of a cell, in the chromosomes

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3
Q

gene

A

a small section of DNA that determines a particular feature/ codes for a particular protein

does this by instructing cells to produce a particular protein

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4
Q

genome

A

the entire DNA of an organism

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5
Q

the nitrogenous bases

A

adenine, thymine, cytosine, guanine

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6
Q

what is DNA made up of

A

two strands of nucleotides - each containing a sugar molecule, phosphate group and linked by a series of paired nitrogenous base- coiled into a double helix

a sugar-phosphate backbone with complementary nitrogenous bases

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7
Q

DNA replication

A
  1. polynucleotide DNA strands separate
  2. each strand is used as a template for the formation of a new DNA strand
  3. DNA polymerase assembles the strands into two new strands according to the base pairing rule
  4. two IDENTICAL DNA molecules are formed -each containing a strand from the parent DNA and the new complementary strand
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8
Q

template strands

A

actually codes for the manufacture of proteins in a cell

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9
Q

triplet code

A

the DNA code is a triplet code, a sequence of 3 bases codes for one amino acid e.g TGT codes for the amino acid cysteine

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10
Q

differences between DNA and RNA

A
  • RNA is single strand, DNA is double helix
  • RNA contains ribose, DNA contains deoxyribose
  • RNA contains the base uracil instead of thymine
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11
Q

two types of RNA

A

mRNA (messenger RNA): forms a copy of the DNA code

tRNA (transfer RNA): carries amino acids to the ribosomes to make the protein

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12
Q

the two stages of protein synthesis

A
  • transcription
  • translation
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13
Q

transcription

A

enzyme unwinds and unzips a section of the DNA helix, allowing RNA polymerase to create a complementary strand of mRNA

The mRNA carries this copied genetic information out of the nucleus to the ribosomes where proteins are assembled based on this code

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14
Q

translation

A

takes place in the ribosomes, the code consists of sets of 3 bases in the mRNA called codons. each codon codes for a particular amino acid

the mRNA molecule attaches to a ribosome. the tRNA molecules each have an anticodon of three bases at one end of their molecule, which is complementary to a particular codon on the mRNA. at the other end of the tRNA molecule is a site where a specific amino acid can attach. the tRNA molecule carries its amino acid to the ribosome where its specific anticodon pairs up with the three bases of the corresponding mRNA codon

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15
Q

mutation

A

a mutation is a rare, random change in genetic material that can be inherited

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16
Q

types of mutations

A
  • duplication
  • deletion
  • substitution
  • inversions
17
Q

duplication mutation

A

nucleotide is inserted twice instead of once, entire base sequence is altered, whole gene is different and will now code for an entirely different protein

18
Q

deletion mutation

A

a nucleotide is missed out, entire base sequence is altered, whole gene is different and will now code for an entirely different protein

19
Q

substitution mutation

A

a different nucleotide is used, triplet of bases in which the mutation occurs is changed and it may code for a different amino acid

20
Q

inversions mutation

A

the sequence of the bases in a triplet is reversed, similar effects to substitution, only one triplet is affected

21
Q

mutagens

A

agents which increase the rate of gene mutations

22
Q

examples of mutagens

A
  • ionising radiation (UV light, X-rays, and gamma rays)
  • chemicals e.g mustard gas, nitrous oxide, chemicals in cigarette smoke
23
Q

natural selection

A

process where certain individuals in a population survive because they are better adapted to their environment. they are more likely to pass on their genes to their offspring

24
Q

the structure of chromosomes

A

each chromosome contains one double-stranded DNA molecule. The DNA is folded and coiled so that it can be packed into a small space. the DNA is coiled around proteins called histones

25
Q

pairs of matching chromosomes are called

A

homologous pairs, carry genes for the same features

26
Q

alleles

A

different forms of a gene

27
Q

two types of alleles

A

dominant and recessive, recessive allele will only show up in appearance if there is no dominant allele present

28
Q

dominant allele

A

allele of a gene that is expressed in the heterozygote

29
Q

recessive allele

A

allele of the gene that is not expressed in the phenotype when a dominant allele of the gene is present

30
Q

homozygous

A

genotype with the same alleles of a gene

31
Q

heterozygous

A

genotype with different alleles of a gene

32
Q

phenotype

A

how a gene is expressed. the ‘appearance’ of an organism resulting from its genotype

33
Q

genotype

A

alleles an organism has for a certain characteristic

34
Q

how is the sex of a person controlled

A

by one pair of chromosomes, XX for female and XY for male

35
Q

mitosis

A

asexual reproduction

when a cell reproduces by splitting to form two daughter cells with identical sets of chromosomes.

cell duplicates DNA then splits into two identical daughter cells (diploid). 1 division

36
Q

when does mitosis occur

A

growth, repair, cloning, and asexual reproduction

37
Q

meiosis

A

sexual reproduction

cell replicates DNA and splits into two daughter cells (diploid), which then each split into another two daughter cells (haploid) with genetically different chromosomes.

meiosis produces four haploid gametes whose chromosomes are not identical

38
Q

evolution

A

inheritance of certain characteristics in a population, over multiple generations, could lead to a change in the whole species

biology (9 decks)

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