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Biology > Unit 6 - Inheritance, Variation And Evolution > Flashcards

Unit 6 - Inheritance, Variation And Evolution Flashcards

1
Q

What is DNA

A

-stands for deoxyribonucleic acid
-contains coded information
-found in nucleus in structures called chromosomes

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2
Q

Structure of DNA

A

-polymer made up of repeating units called nucleotides
-each nucleotide consists of one sugar molecule, one phosphate molecule and one base
-sugar and phosphate molecules alternate
-one of 4 different bases join to each sugar (A, T, C, G)
-each base links to a base on the opposite strand
-A always pairs with T and C and G
-the order of the bases that decide the order of amino acids in a protein
-a double helix structure

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3
Q

What is a gene

A

-A gene is a small section of DNA on a chromosome
-each gene codes for a particular sequence of amino acids to make a specific protein

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4
Q

What is a genome

A

-Genome of an organism is the entire genetic material of that organism
-the whole human genome has now been studied and has great importance for medicine in the future

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5
Q

Human genome project important and what it is discovering

A

-allows scientists to identify genes in the genome that are linked to different types of diseases
-knowing which genes are linked to inherited diseases so we can develop effective treatments for them
-use them in tracing human migration patterns from the past

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6
Q

What is protein synthesis

A

-made in cytoplasm in ribosomes
-to make proteins, ribosomes use the code in the DNA (in the nucleus) and transfer it to the ribosomes
-this is done using a molecule called mRNA which acts as a messenger between the DNA and ribosomes
-amino acids would be brought to ribosome in correct order by carrier molecules
-the amino acids would then be joined together to make correct protein

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7
Q

How does the structure of DNA affect the protein made

A

-when a chain of amino acids has been assembled it folds into a unique shape which allows the protein to perform a specific task

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8
Q

Different examples of proteins and their functions

A

-enzyme (biological catalysts to speed up chemical reactions in the body)
-hormones (carry messages around the body)
-structural proteins (physically strong, collagen is an example that strengthens connective tissue)

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9
Q

What are mutations

A

-Changes to genetic code
-sometimes inherited or occur spontaneously
-most do not alter the protein and most have very little effect
-A few mutations code for an altered protein with a different shape. An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
-mutations change the sequence of the DNA bases in a gene which produces a genetic variant
-if there’s a mutation in non coding DNA it can later how genes are expressed

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10
Q

Different types of mutations that can occur

A

-insertions
-deletions
-substitutions

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11
Q

What is an insertion mutation

A

-Where a new base is inserted into a DNA base sequence where it shouldn’t be
-insertions change you way the groups of three bases are read which can change the amino acid they are coded for

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12
Q

What is a deletion mutation

A

-When a random base is deleted from the DNA base sequence
-they change the way the base sequence is read and have knock on effects further down the sequence

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13
Q

What is a substitution mutation

A

-When a random base in the DNA base sequence is changed into a different base

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14
Q

What is the relationship between DNA and proteins

A

DNA contains genes, each gene codes for a particular sequence of amino acids which are put together to make a protein

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15
Q

What is sexual reproduction

A

-Involves the fusion of male and female gametes
-Because there are two parents the offspring contains a mixture of their parents genes which leads to variation
-involved meiosis

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16
Q

What are gametes are fused in males and females in animals and plants

A

Animals = sperm and egg cell
Plants = pollen and egg cells

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17
Q

What is asexual reproduction

A

-Involves only one parent
-no fusion of gametes
-genetically identical offspring so no variation
-mitosis is involved (one cell divides into two identical cells)
-bacteria some plants and animals reproduce asexually

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18
Q

What is meiosis

A

-before it starts to divide it duplicates genetic information
-cell divides twice
-you get four gametes each with a single set of chromosomes
-each gamete is genetically different from each other

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19
Q

Where does meiosis occur

A

In reproductive organs where gametes are being made

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20
Q

What is mitosis

A

-DNA is copied
-cell must increase amount of mitochondria and ribosomes
-chromosomes are pulled apart
-nucleus divides
-cell membrane and cytoplasm divide
-two new daughter nuclei produced
-genetically identical cells

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21
Q

Advantages of sexual reproduction

A

-produces variation in offspring
-if environments changes variation gives a survival advantage by natural selection
-natural selection can be speeded up by humans in selective breeding to increase food production

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22
Q

Advantages of asexual reproduction

A

-only one parent needed
-more time and energy efficient as do not need to find a mate
-faster than sexual reproduction
-many identical offspring can be produced when conditions are favourable

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23
Q

Examples of organisms reproducing sexually and asexually

A

-malaria parasites reproduce asexually in the human host but sexually in the mosquito
-fungi reproduce asexually by spores but reproduce sexually to give variation
-many plants reproduce seeds sexually but also asexually by runner such as strawberry plants

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24
Q

What is a gamete

A

Reproductive sex cell

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25
Q

What are chromosomes

A

-thin strands of DNA
-carry genetic information from cell to cell
-they are subdivided into genes
-23 pairs of chromosomes in each human body cell

26
Q

What is an allele

A

-different versions of the same gene
-For example, the gene for eye colour has an allele for blue eye colour and an allele for brown eye colour

27
Q

What are dominant or recessive alleles

A

-A dominant allele only needs to be inherited from one parent in order for the characteristic to show up in the phenotype
-A recessive allele needs to be inherited from both parents in order for the characteristic to show up in the phenotype

28
Q

What is homozygous and heterozygous

A

-homozygous = alleles are both identical for the same characteristic, for example AA or aa
-heterozygous= alleles are both different for the same characteristic, for example Aa

29
Q

What is the genotype

A

-the collection of alleles that determine characteristics and can be expressed as a
phenotype

30
Q

What is the phenotype

A

-The visible characteristics of an organism which occur as a result of multiple genes

31
Q

What are the female and male chromosomes

A

Female = XX (this combination allows female characteristics to develop)
Make= XY (Y chromosomes cause male characteristics)

32
Q

Examples of characteristics which are controlled by a single gene

A

-fur colour in mice
-red green colour blindness in humans

33
Q

What is cystic fibrosis and what is it caused by

A

-disorder of cell membranes ( lots of sticky mucus in air passages)
-caused by a recessive allele which means people with only one copy won’t have the disorder but they are carriers

34
Q

What is polydactyl and what is it caused by

A

-having extra fingers and toes
-caused by dominant allele so can be inherited if just one parent carries the allele

35
Q

What is embryo screening and what does it do

A

-during IVF before embryos are implanted in the womb you can remove a cell from each embryo and analyse its genes
-genetic disorders can then be detected

36
Q

Advantages and disadvantages of embryo screening

A

A= stop people suffering , treating disorders costs the government and taxpayers money, there are laws to stop it going too far (people can’t choose sex of baby unless for health reasons)
D= implies that genetic problems are undesirable which could cause prejudice, may come a point where everyone wants to screen embryos so they can pick the most desirable one (blue eyes, blond hair), expensive

37
Q

Three conclusions reached by Mendel

A

-characteristics in plants are determined by hereditary units
-hereditary units are passed on to offspring unchanged from both parents (one unit from each parent)
-hereditary units can be dominant or recessive

38
Q

Why didn’t people accept Mendels work

A

-no one had any background knowledge to properly understand his findings
-after his death people realised the significance of it
-his work was a starting point that other scientists contributed to understanding the genes we have today

39
Q

What is variation and the two types

A

-Differences in the characteristics of individuals in a population
-genetic variation and environmental variation

40
Q

What causes variations

A

-genes they have inherited (genetic)
-conditions in which they have developed (environmental)
-combination of genes and the environment

41
Q

Do mutations have an effect on the phenotype

A

-most have no effect on protein the gene codes for so most have no effect on phenotype
-some have small influence and only alter characteristics slightly
-very rarely mutations can result in a new phenotype, if the new phenotype is suited to an environmental change it can lead to rapid change in the species

42
Q

What is evolution

A

Change in the inherited characteristics of a population over time through a process of natural selection which may result in a formation of new species

43
Q

What is the theory of evolution

A

All of todays species of living things have evolved from simple life forms that first developed more than three billion years ago

44
Q

What is natural selection (Charles Darwin’s ideas)

A

-referred to as survival of the fittest
-process where organism that are better adapted to an environment will survive and reproduce
-they will pass on genes to make their offspring successful
-beneficial characteristics become more common in population and the species evolve

45
Q

How did Charles Darwin come up with his theories

A

As a result of a observations on an around the world expedition backed by years of experimentation and discussion and linked to developing knowledge of geology and fossils he suggested the theory of evolution by natural selection

46
Q

Why was the theory of evolution only gradually accepted

A

-the theory challenged the idea that god made all the animals and plants that live on earth
-there was insufficient evidence at the time the theory was published to convince many scientists
-the mechanism of inheritance and variation was not known until 50 years after the theory was published

47
Q

What was the book called that Charles Darwin published his ideas in

A

On the origin of species (1859)

48
Q

What is environmental variation

A

-differences between members of same species that have been caused by environment or conditions something lives in
-examples = suntan, scars, accent

49
Q

What is speciation

A

-phenotype can change so much because of natural selection that completely new species forms
-happens when population of the same species change enough to become reproductively isolated this means they can’t interbred to produce fertile offspring

50
Q

What is extinction and what causes it

A

-when no individuals of a species remain

-environment changes too quickly (destruction of habitat)
-new predator kills them (humans hunting them)
-new disease kills them
-can’t compete with another species for food
-catastrophic event (volcanic eruption)

Example = dodos (humans hunted them )

51
Q

What was the work of Jean Baptiste Lamarck

A

-argued that changes that an organism acquires during it lifetime will be passed onto its offspring
-for example if a rabbit used its legs to run a lot to scape predators that it’s legs would get longer, the offspring of that rabbit will be born with longer legs
-his hypothesis was eventually rejected

52
Q

What was the work of Alfred Wallace

A

-he published joint writing with Darwin which prompted Darwin to publish ‘on the origin of species’
-worked worldwide gathering evidence for evolutionary theory
-best known for his work on warning colouration in animals and his theory of speciation

53
Q

One cause of genetic variation in a population other than mutations

A

Sexual reproduction

54
Q

What is selective breeding

A

-process by which humans breed plants and animals for particular genetic characteristics
-humans have been doing this for hundreds of years
-they are selectively bred to develop features that are useful or attractive

55
Q

Examples of selective breeding

A

-animals that produce more meat or milk
-crops with disease resistance
-dogs with gentle nature
-large or unusual flowers

56
Q

Process of selective breeding

A

-choosing parents with desired characteristics from a mixed population
-breed them together
-select the best offspring and breed them together
-continue this over several generations until all the offspring show the desired characteristic

57
Q

Disadvantages of selective breeding

A

-can cause Inbreeding (reduction in number of different allele) where some breeds are particularly prone to disease or inherited defects
-if new disease appears there is little variation, so if one of them is killed by it the others are likely to as well

58
Q

What is genetic engineering and an example

A

-Process which involved modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
-plants crops have been genetically engineered to be resistant to diseases or to produce bigger better fruits

59
Q

How have bacteria been genetically engineered

A

-to produce useful substances such as human insulin to treat diabetes

60
Q

Process of genetic engineering

A

-useful gene is isolated (cut) from one organisms genome using enzymes and is inserted into a vector
-this vector is usually a virus or bacterial plasmid depending on type of organism that the gene is being transferred to
-when vector is introduced to target organism the useful gene is inserted into its cells

61
Q

Advantages and disadvantages of genetically modified crops

A

A= can increase yield making more food, people in developing nations often lack nutrients so can be engineered to contain nutrients, GM crops are being grown in some places without any problems
D= affect number of wildflowers and therefore insects around crops (reducing farmland biodiversity), concerns about safety and the effects of eating them on human health- they may develop allergies

Biology (6 decks)

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