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LS - Entire Sections > Genetics > Flashcards

Genetics Flashcards

1
Q

What is genetics?

A
  • a branch of biology that studies heredity and variation in organisms
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2
Q

What does genetics try to explain?

A
  • both the similarities and differences between parents and their offspring
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3
Q

Who was the ‘father of genetics’?

A
  • Gregor Mendel
  • an Austrian monl
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4
Q

What realisation did Mendel have?

A
  • that ‘something’ is passed on from parent to offspring
  • that sexual reproduction combines these ‘somethings’ from each parent
  • to produce offspring which are unique, yet the same
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5
Q

What are the factors passed from parent to offspring?

A
  • genes
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6
Q

What is each chromatid made up of?

A
  • 1 helical DNA molecule
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7
Q

What is each DNA molecule made up of?

A
  • a series of genes
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8
Q

What is a gene?

A
  • a section of DNA (series of nucleotides/bases) that controls a hereditary characteristic (trait)
  • ie it is the basic unit of heredity in living organisms
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9
Q

What do nearly all somatic cells have?

A
  • an exact copy of all the genes in that organism
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10
Q

Why does each cell contain 2 of each kind of gene (before replication)?

A
  • because there are 2 of each kind of chromosome (paternal and maternal)
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11
Q

What is a gene pool?

A
  • the set of all genes, or genetic information, in a population of sexually reproducing organisms
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12
Q

What does a large gene pool indicate?

A
  • high genetic diversity
  • increased chances of survival
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13
Q

What does a small gene pool indicate?

A
  • low genetic diversity
  • increased possibility of extinction
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14
Q

How active are genes?

A
  • only the genes that are needed are activated and the other suppressed
  • different genes are activated in different cells, creating the specific proteins that give a particular cell type its character (e.g. bone cells, brain cells, skin cells etc.)
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15
Q

What are ‘housekeeping genes’?

A
  • genes that are active in many types of cells, making proteins needed for basic functions
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16
Q

What are hox genes?

A
  • master control genes that determine the way in which the body develops from a single zygote
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17
Q

What are alleles responsible for?

A
  • genes responsible for controlling different versions of a trait/characteristic found in the same locus on homologous chromosomes
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18
Q

What is the control of genes called?

A
  • epigenetics
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19
Q

What are alleles?

A
  • one of two or more forms of a gene
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20
Q

How are alleles passed from parent to offspring?

A
  • by way of chromosomes in the gametes that are made by the process of meiosis in the sex organs
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21
Q

What happens to the gametes during fertilisation?

A
  • a male gamete fuses with a female gamete to form a diploid zygote
  • this divides by mitosis to form an entire new organism made up of cells
  • each with the same set of chromosomes and alleles as in the zygote
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22
Q

What is a genotype?

A
  • a genotype is made up of all the genes an organism carries on its chromosomes which it has inherited from its parents
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23
Q

What is a phenotype?

A
  • the physical appearance of an organism
  • partly programmed by genes, its genotype, and also external factors such as exercise, diet and environment
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24
Q

When is an organism homozygous for a particular trait?

A
  • if the pair of alleles at a locus are the same
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25
Q

When is an organism heterozygous for a particular trait?

A
  • if the pair of alleles at a locus are different
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26
Q

What are the kind of alleles in a heterozygous pairing?

A
  • dominant
  • recessive
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27
Q

What is a dominant allele?

A
  • the trait that is expressed in the offspring
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28
Q

What is a recessive allele?

A
  • the trait that is suppressed in the presence of the dominant allele and not expressed in the offspring
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29
Q

What is a monohybrid cross?

A
  • a cross between parents with different alleles for a single gene
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30
Q

How are generations shown in genetic diagrams?

A
  • P1 - parent generation
  • F1 - first filial generation of offspring
  • F2 - second filial generation of offspring
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31
Q

What is a punnet square?

A
  • an easy way to represent a cross between 2 organisms for any number of characteristics for which the parental genotypes are known
32
Q

What does a punnet square do?

A
  • predicts the probability of the offspring’s genotype and phenotype
  • is the basic tool used for Mendelian genetics
33
Q

What is complete dominance?

A
  • a characteristic that is fully expressed in the phenotype of a heterozygous organism
34
Q

What is stated in Mendel’s law of segregation?

A
  • during meiosis, allele pairs separate (segregate) so that the gametes have a single allele for each characteristic
35
Q

What is stated in Mendel’s law of dominance?

A
  • in a cross of parents that are pure for contrasting traits, only the dominant trait will appear in the phenotype
  • recessive alleles will always be masked by dominant alleles
36
Q

What is stated in Mendel’s law of independent assortment?

A
  • the alleles of different genes segregate randomly and independently of one another during gamete formation
37
Q

Which pair of chromosomes are the sex chromosomes/gonosomes?

A
  • pair 23
38
Q

What sex chromosome combination codes for a female?

A
  • XX
39
Q

What sex chromosome combination codes for a boy?

A
  • XY
40
Q

What is the sex of an organism determined by?

A
  • the presence or absence of the Y chromosome
41
Q

What is the inheritance of sex a special form of?

A
  • inheritance of sex is a special form of monohybrid inheritance
42
Q

How is the Y chromosome structured in relation to alleles?

A
  • the Y chromosome is very short and has very few alleles on it other than those responsible for ‘maleness’
43
Q

How is the X chromosome structured in relation to alleles?

A
  • the X chromosome is much longer and can carry many alleles along its length in addition to those for ‘femaleness’
44
Q

What are x-linked genes/sex-linked?

A
  • the alleles that are carried on the non-homologous part of an X chromosome
45
Q

What are some examples of sex-linked diseases?

A
  • cleft palate
  • diabetes insipidus
  • red-green colour blindness
  • haemophilia
  • muscular dystrophy
46
Q

Why do certain genetic diseases seem to occur more often in males than in females?

A
  • because the male has only 1 X chromosome
  • so if a gene mutates or if a gene for a disease is present on this X chromosome, the male will get the genetic disease
  • if the gene is recessive, it will only be expressed in the female if both X chromosomes have the allele
47
Q

What are examples of diseases caused by a recessive sex-linked allele on the X-chromosome?

A
  • red-green colour-blindness
  • haemophilia
48
Q

What is the main characteristic of polygenic inheritance?

A
  • there is more than one pair of alleles responsible for a single trait
49
Q

How are the complex traits found in polygenic inheritance determined?

A
  • they are determined by the interaction of many different alleles
  • each having small individual effects on the offspring
  • resulting in a range of phenotypes
50
Q

What is continuous variation?

A
  • graduations of a characteristic in a phenotype
  • e.g. height in humans
51
Q

How does continuous variation work?

A
  • the more pairs of alleles that control a characteristic, the greater the number of possible combinations and the greater the variety of phenotypes
  • each phenotype differs slightly from the next, forming a graduated series
52
Q

What are some examples of continuous variation in polygenic inheritance?

A
  • height
  • skin colour
  • metabolic rate
  • longevity
53
Q

What is a mutation?

A
  • a sudden change in the genetic makeup (DNA) of an organism
54
Q

How does a gene mutation occur?

A
  • from a change in the sequence of nucleotides in a DNA molecule
  • causing a change in the information the gene gives to the cell
  • i.e. the codons will be altered which will result in a faulty protein or no protein at all being made
55
Q

What are mutagens?

A
  • factors that increase the rate of mutations
56
Q

What are some examples of environmental mutagens?

A
  • ionising radiation (ultraviolet light and X-rays)
  • mutagenic chemicals
  • viruses
  • micro-organisms
57
Q

What are the different types of cell mutations?

A
  • somatic mutations
  • gametic mutations
58
Q

What are the characteristics of somatic mutations?

A
  • occur in body cells
  • not transmitted to the next generation
  • can cause cells to become malignant, resulting in cancer
59
Q

What are the characteristics of gametic mutations?

A
  • occur in the reproductive organs (ovaries, testes, anthers, embryo sacs)
  • produce changes to the genes in the gametes
  • these germ-line mutations may lead to variation in the offspring
  • eventually by accumulating these changes, a new species may evolve, a process called speciation
  • may lead to hereditary diseases
60
Q

What are the 3 kinds of mutations?

A
  • neutral mutations
  • beneficial mutations
  • harmful mutations
61
Q

What are the effects of neutral mutations?

A
  • they do not affect the life of the organism
62
Q

When do beneficial mutations occur most often and why?

A
  • amongst viruses and bacteria
  • due to their rapid reproduction rate
  • e.g. new multi-resistant bacteria that have mutated to become resistant to antibiotics
63
Q

How does natural selection occur as a result of beneficial mutations?

A
  • when a mutation leads to a change in the phenotype
  • resulting in organisms adapting better to new or unfavourable conditions
  • allowing them to survive and breed more successfully than the rest of the population
64
Q

What happens as a result of natural selection and beneficial mutations?

A
  • in time the whole population will have the new genotype and a new species will have been formed
  • i.e. speciation has occurred
65
Q

How are harmful mutations usually inherited?

A
  • as autosomal recessive traits
66
Q

What does autosomal mean?

A
  • relates to chromosomes that are not sex chromosomes
  • i.e. numbers 1 to 22
67
Q

How do harmful mutations occur?

A
  • the heterozygous parents each have one normal copy of the gene and one mutated, non-functional copy
  • the homozygous recessive individuals exhibit the disorder because both gene copies are non-functional and the correct gene product, a protein, is missing
68
Q

What is a genome?

A
  • the complete set of genetic instructions necessary to create an organism
69
Q

What is the Human Genome Project (HGP)?

A
  • an international scientific research project set up in 1990
70
Q

What are the primary goals of the HGP?

A
  • to determine the sequence of chemical base pairs which make up human DNA (DNA sequencing)
  • to identify and map all the genes of the human genome from both a physical and functional point of view
71
Q

What is the importance of learning more about the functions of genes and proteins?

A
  • it has a major impact on the fields of medicine, biotechnology and life sciences
  • e.g. genes have been discovered that are linked to Alzheimer’s, bad cholesterol and heart disease and breast cancer association
72
Q

What are genetic counsellors?

A
  • health professionals with specialised graduate degrees and experiences in the areas of medical genetics and counselling
73
Q

What do genetic counsellors do?

A
  • provide information and support to families who have members with birth defects or genetic disorders
74
Q

What sort of issues could be discussed by genetic counsellors?

A
  • whether a couple should have children if both are carriers of a faulty gene
  • if artificial insemination is a practical alternative to the problem
  • if in vitro fertilisation is a possible option
  • whether cousins should contemplate having children
75
Q

What does a family pedigree show?

A
  • the pattern of inheritance of a particular characteristic
76
Q

What does a family tree show?

A
  • the genotypes and phenotypes of several generations of individuals in a family
77
Q

How are family trees useful?

A
  • can be used to predict whether a couple is likely to pass on a genetic disorder

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