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Biology Content > Genetic Information, Variation, and Relationships Between Organisms > Flashcards

Genetic Information, Variation, and Relationships Between Organisms Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the DNA molecules like in eukaryotic cells?

A
  1. long
  2. linear
  3. associated with proteins called histones
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2
Q

What are the DNA molecules like prokaryotic cells?

A
  1. short
  2. circular
  3. not associated with proteins
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3
Q

What is a gene?

A

A sequence of bases on DNA which determines the amino acid sequence of a polypeptide.

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4
Q

What is a locus?

A

A gene occupies a fixed positions on a particular DNA molecules.

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5
Q

What is an allele?

A

Different versions of genes.

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6
Q

What is a codon?

A

A sequence of 3 bases, which code for a specific amino acid.

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7
Q

What are characteristics of DNA and what does each characteristic mean?

A
  1. universal - for all living things.
  2. non-overlapping - each triplet is read separately.
  3. degenerate - some amino acids have more than one triplet code.
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8
Q

What are exons?

A

Exons are sequences within a gene that code for amino acid sequences.

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9
Q

What are introns?

A

Introns are non-coding sequences.

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10
Q

Name 5 characteristics of mRNA.

A
  1. single stranded
  2. linear chain
  3. longer chain / has more nucleotides
  4. complementary to genetic sequence of a gene
  5. unpaired bases in codons
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11
Q

Name 5 characteristics of tRNA.

A
  1. single stranded but folded into a clover shape
  2. contains hydrogen bonds
  3. has an anticodon
  4. has a specific amino acid attachment site
  5. all similar lengths
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12
Q

What is a genome?

A

The complete set of genes in a cell.

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13
Q

What is a proteome?

A

The full range of proteins that a cell is able to produce.

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14
Q

In 3 points, describe protein/polypeptide synthesis.

A
  1. The sequence of nucleotides on a gene on DNA acts as a template.
  2. A complementary copy is transcribed onto mRNA in the nucleus.
  3. At the ribosomes the mRNA acts as a template that is translated into a chain of amino acids using complementary tRNA which carry specific amino acids which are linked together.
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15
Q

Describe the process of transcription.

A
  1. hydrogen bonds between base pairs are broken.
  2. One strand acts as template to make an mRNA copy.
  3. Free RNA nucleotides join their complementary pairing ( adenine with uracil, cytosine with guanine, thymine with adenine and guanine with cytosine).
  4. RNA polymerase joins adjacent nucleotides together with a phosphodiester bond.
  5. RNA polymerase continues until it reaches a stop codon.
  6. Introns are spliced out of pre-mRNA by an enzymes, leaving mature mRNA.
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16
Q

Describe the process of translation.

A
  1. mRNA attaches to a ribosomes.
  2. tRNA anticodons binds to complementary codons on mRNA.
  3. tRNA brings a specific amino acid.
  4. two tRNA can bind simultaneously.
  5. adjacent amino acids undergo a condensation reaction and form a peptide bond (using ATP).
  6. first tRNA detaches and the ribosome moves to the next codon.
  7. This continues, forming a polypeptide until a stop codon is reached and the ribosome detaches.
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17
Q

What is a diploid zygote?

A

A diploid zygote is 2 of each type of chromosome.

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18
Q

What is a haploid gamete?

A

A haploid gamete is 1 of each type of chromosome.

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19
Q

What is the purpose of meiosis 1?

A
  1. To separate homologous pairs.
  2. To introduce genetic variation.
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20
Q

What is the purpose of meiosis 2?

A

Separation of sister chromatids, four haploid cells are produced, each with half the diploid number of chromosomes.

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21
Q

How many divisions are in meiosis?

A

2

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22
Q

Which stage does crossing over occur in?

A

Prophase 1.

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23
Q

Describe the process of crossing over.

A
  1. Homologous pairs of chromosomes associate and form a bivalent.
  2. Chiasmata forms.
  3. Equal lengths of non-sister chromatids or alleles are exchanged.
  4. Producing a new combination of alleles.
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24
Q

Describe the process of independent/random segregation.

A
  1. In metaphase 1, homologous pairs line up either side of the equator.
  2. It is completely random which side of the equator the maternal and paternal chromosomes line up on.
  3. When they are separated, one of each pair ends up in a daughter cell.
  4. This ‘shuffling’ leads to different combinations of the maternal and paternal chromosomes in daughter cells.
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25
Q

Compare mitosis and meiosis.

A
  1. Mitosis has the same number of chromosomes, whereas meiosis has half the number of chromosomes.
  2. Mitosis chromosomes are genetically identical, whereas meiosis chromosomes are genetically different.
  3. Mitosis results in two daughter cells, whereas meiosis results in four daughter cells.
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26
Q

Define fertilisation.

A

Random mating with random gametes, this results in random fusion of gametes and produces new allele combinations. Mutations may occur.

27
Q

Define mutation.

A

Changes in the base sequence of chromosomes, resulting in a new allele. They can spontaneously arise in DNA replication.

28
Q

Describe the substitution mutation.

A

One base is changed for another during DNA replication. Only one codon with the mutation is affected.

29
Q

Describe the deletion mutation.

A

One base is left out during DNA replication. This results in a frame shift - all the codons after the mutation are affected.

30
Q

Describe the insertion mutation.

A

An extra base is added during DNA replication. This results in a frame shift - all the codons after the mutation are affected.

31
Q

Why can a mutation occur and yet there is no change in amino acid.

A
  1. Due to genetic nature of the genetic code, not all base substitutions cause a change in the sequence of encoded amino acids. This means that more than one codon codes for the same amino acid.
  2. If mutation is in the intron, amino acid will not change.
32
Q

Define mutagenic agents.

A

Mutagenic agents can increase the rate of gene mutations

33
Q

What is non-disjunction.

A

When chromosomes are not properly separated and are not shared equally between the daughter cells in metaphase and anaphase. This results in daughter cells having a different number of chromosomes.

34
Q

Define genetic diversity.

A

The total number of different alleles that exist in a population.

35
Q

Define population.

A

A group of organisms of one species living in a particular habitat.

36
Q

Define species.

A

A group of organisms that can breed with each other to produce fertile offspring. They have the same number of chromosomes.

37
Q

State the seven things which may affect genetic diversity of a population.

A
  1. Population size - smaller populations generally have a lower genetic diversity.
  2. Inbreeding - reduces genetic diversity.
  3. Migration - increases genetic diversity.
  4. Mutations - increases genetic diversity.
  5. Genetic bottlenecks - reduces genetic diversity.
  6. Founder effect - reduces genetic diversity.
  7. Natural selection - increases the frequency of beneficial alleles.
38
Q

Describe how genetic bottlenecks reduce genetic diversity.

A
  1. A random event which causes a big reduction in a population.
  2. A large number of population die before reproducing.
  3. This reduces the number of different alleles in the gene pool.
  4. The survivors and a larger population is produced from a few individuals with a smaller genetic diversity.
39
Q

Describe how the founder effect affects genetic diversity.

A
  1. A few organisms from a larger original population start a new population.
  2. The new population have less variety of alleles in the initial gene pool.
  3. These few individuals reproduce together to establish a larger population but with a different frequency of alleles than the original population.
40
Q

Describe the process of natural selection.

A
  1. Mutation - a gene mutates, some mutations can be harmful (more likely to die), some mutations can be beneficial (increasing chance of survival).
  2. Advantage and survival - alleles are better posed to the environment and therefore organisms are more likely to survive.
  3. Reproduction - more organisms which have advantageous alleles are more likely to reproduce and inherit advantageous allele. Next generations are better adapted to the environment.
  4. Change in allele frequency - passing on alleles to next generation, so multiple generations cause frequency of the allele to increase.
41
Q

Describe directional selection using antibiotic resistance.

A
  1. Individuals with alleles for an extreme type are more likely to survive and reproduce.
  2. Some bacteria have alleles that give them resistance to an antibiotic.
  3. The normal population of bacteria are killed by the antibiotic.
  4. Resistant bacteria survive and reproduce without competition passing on the allele for antibiotic resistance to their offspring.
  5. After some time, most of the population will have the antibiotic resistance allele.
42
Q

Describe stabilising selection using human birth weight as an example.

A
  1. Individuals with alleles for the middle of the range are more likely to survive and reproduce.
  2. Small babies find it hard to maintain their body temperature so less likely to survive.
  3. Large babies are also less likely to survive.
  4. So conditions most favourable for medium sized babies.
  5. The weight of human babies shifts towards the middle of the range.
43
Q

What are anatomical, physiological and behavioural adaptions?

A
  1. Anatomical adaptations are structural features.
  2. Physiological adaptations are processes within organisms.
  3. Behavioural adaptations are the way an organism acts.
44
Q

Define taxonomy.

A

The science of classification.

45
Q

What is a phylogenetic classification system?

A

A phylogenetic system attempts to arrange species into groups based on their evolutionary origins and relationships.

46
Q

Define hierarchal.

A

Smaller groups are placed within larger groups with no overlap between groups.

47
Q

What is the order of the classification system?

A
  1. Domain.
  2. Kingdom.
  3. Phylum.
  4. Class.
  5. Order.
  6. Family.
  7. Genus.
  8. Species.
48
Q

Define the binomial system.

A

Includes the genus and species name.

49
Q

State 3 ways in which evolutionary relationships can be clarified and how?

A
  1. DNA/mRNA sequences - more similarities mean more closely related.
  2. Amino acid sequences - the more similarities more closely related.
  3. Immunology - similar proteins will bind the same antibodies.
50
Q

What do phylogenetic trees show?

A

They show evolutionary relationships. A branch is a common ancestor.

51
Q

What is courtship behaviour?

A

It is carried out by organisms to attract a mate of the right species. Courtship behaviours are unique to each species, which allows one species to successfully identify individuals of their own species.

52
Q

How does courtship ensure successful reproduction?

A

Enables individuals to recognise others of their own species and individuals of the opposite sex. It also synchronises mating behaviour - mating occurs only when the individual is sexually mature and in season.

53
Q

How does courtship increase the survival of the offspring?

A

Formation of pair bonds - 2 parents looking after the offspring increases its survival.

54
Q

Define biodiversity.

A

The variety of organisms living in an area. It varies in different parts of the world ; it is greatest at the equator and decreases towards the poles.

55
Q

Define a habitat.

A

The place where organisms live.

56
Q

Define a community.

A

All the populations of different species in a habitat.

57
Q

Define species richness.

A

A measure of the number of different species in a community. It can be calculated by taking random samples of a community and counting the number of different species.

58
Q

Define agriculture.

A

The cultivation of soil to grow crops.

59
Q

State 4 practices in agriculture and why each reduces biodiversity.

A
  1. Removing woodlands/hedgerows - Less habitats, less variety of food sources.
  2. Using pesticides - killing insect species ; reduction in the variety of food sources of organisms higher up the food chain.
  3. Using herbicides - kills species of weeds ; reduction in the variety of food types for herbivores.
  4. Growing one type of crop (monoculture) - less variety in food sources ; less variety of habitats.
60
Q

Define conservation.

A

A balance between the need for agriculture and maintaining biodiversity.

61
Q

State 3 ways in which there may be conversation in terms of biodiversity and describe how.

A
  1. Endangered species are given legal protection - restrictions on hunting/fishing during breeding season or a limitation on the size of fish caught.
  2. The Environmental Stewardship scheme - encourages farmers to conserve biodiversity, for example replanting hedgerows.
  3. Sites of special interest - protected under the Wildlife and Countryside Act 1981.
62
Q

What is the student T test?

A

A statistically test that analyses the differences between two mean values to see if they are significantly different.

63
Q

In the student T test, what does P < 0.05 (5%) suggest.

A

The differences are significant.

64
Q

In the student T test, what does P > 0.05 (5%) suggest.

A

The differences are not significant.

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