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biology > D3.2 - inheritance > Flashcards

D3.2 - inheritance Flashcards

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1
Q

autosomal

A

not associated with a sex chromosome

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2
Q

gene pool

A

all the genes and their different alleles, present in a population

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3
Q

What is the pattern of inheritance common to all eukaryotes with a sexual life cycle?

A
  • Production of haploid gametes in parents and their fusion to form a diploid zygote.
  • A diploid cell has 2 copies of each autosomal gene, because it inherits one of each autosomal chromosome from each parent.
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4
Q

What is a gene?

A

A heritable factor that consists of a length of DNA and which influences a specific characteristic

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5
Q

What is an allele?

A

A specific form of a gene with slight difference in base sequence compared with another allele for the same gene

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6
Q

How are new alleles formed?

A

New alleles are formed by mutation

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7
Q

What is a genotype?

A

The combination of alleles inherited by an organism

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8
Q

What is the difference between homozygous and heterozygous genotypes?

A

Homozygous genotype - have 2 of the same alleles.
Heterozygous genotype - have 2 of the different alleles.

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9
Q

Why is there a difference in the number of alleles that occur in a gene pool compared with the number that and individual inherits?

A

Single -nucleotide polymorphisms form multiple alleles, which occur in genomes within a population and therefore occur in a gene pool.
- There is a different allele for each SWP combination that occurs with in a gene.
However, an individual will only inherit one or two different alleles. This is because an allele is present at a particular locus on one type of chromosome. Individuals inherit one type of each chromosome from 3ach of their parents.

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10
Q

What is a phenotype?

A

Observable traits of an organism resulting from genotype and environmental factors.

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11
Q

What are the 3 causes of human traits?

A
  1. Genotype
  2. Environmental factors
  3. Combination of genotype and environmental factors
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12
Q

What are some examples of how the genotype can cause human traits?

A
  • eye colour
  • blood group
  • hair colour at root
  • natural shape of earlobe
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13
Q

What are some examples of how the interaction of genotype and the environment can cause human traits?

A
  • height
  • weight
  • skin colour
  • sporting achievement
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14
Q

What are some examples of how environmental factors can cause human traits?

A
  • tattoos
  • scars
  • language spoken
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15
Q

What is phenotype plasticity?

A

The capacity to develop traits suited to the environment experienced by an organism, by varying patterns of gene expression.

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16
Q

What is the mode of action and the permanence?

A
  • Not due to change in genotype
  • Changes in traits may be reversible during the lifetime of an organism
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17
Q

What are continuous variables?

A
  • No discrete categories
  • Many possible phenotypes
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18
Q

What are discrete variables?

A
  • Distinct categories
  • Few possible phenotypes
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19
Q

What are the effects of the environment on continuous and discrete variables?

A

Continous - strongly influenced by environment
Discrete - unaffected by the environment

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20
Q

How are genes involved in continuous and discrete variables?

A

Continuous - controlled by multiple genes (polygenic)
Discrete - controlled by 1 or few genes

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21
Q

What are the causes of continuous variation?

A

Polygenic inheritance and environmental factors

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22
Q

What is polygenic inheritance?

A

When 2 or more genes influence the expression of one trait

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23
Q

Why is there variation in human skin colour?

A
  • Skin colour is impacted by polygenic inheritance and environmental factors.
  • 4 genes contribute to human skin colour, each of which has alleles that deposit different amounts of melanin into the skin.
  • There are many possible combinations of alleles present in an individual.
  • The additive effects of the fourgenes mean there are many possible amounts of melanin that may be deposited into a person’s skin through genetic factors.
  • However, people’s shin yhour and changes due to sun exposure, which causes more melanin to be deposited and therefore a darkening of the shin. The greater the sun exposure, the more melanin is added.
24
Q

What are the reasons for variation in human height?

A
25
Q

Outline the causes of variation in one example of continous variation in humans.

A
  • One example of continous variation in humans is height or skin colour.
  • With continous variation, any level of phenotype is possible.
  • Polygenic inheritance is the combined effect of more than I gene on a trait.
  • There are additive effects on the trait of alleles on multiple genes.
  • Environmental factors can also cause continuous variation, such as sunlight affecting skin colour.
26
Q

Why are flowering plants, such as peas, well-suited to study inheritance?

A
  • Produce male and female gametes on the same plant, allowing self-pollination and self-fertilization.
  • Pollination is essential for carrying out a cross because pollen contains male gametes and female gametes are located in the ovary.
27
Q

How are flowering techniques used commercially?

A

Genetic crosses are widely used to breed new varieties of crop or ornamental plants.

28
Q

Why are flowering plants well suited to study inheritance over multiple generations?

A

The reactive ease with which pollination can be controlled means multiple generations of plant inheritance can be studied.

29
Q

What are the different generations within an inheritance study called?

A

P generation - parental generations, with only pure-breeding individuals (homozygtes)
F1 generation - offspring of the cross between individuals in the P generations
F2 - offspring resulting from the cross between two individuals of the F1 generations.

30
Q

What is a dominant allele?

A

Allele that is always expressed in the phenotype.
- It can be a homozygous dominant genotype (AA) or a heterozygous genotype (Aa) and it will produce the same phenotype as they contain the dominant allele.

31
Q

What is a recessive allele?

A

Allele that is expressed if no dominant allele is present.
(aa)

32
Q

What is a Punnett grid?

A

A diagram used to show how alleles within an individuals genotype are split into gametes, plus the combination of alleles that could occur in the genotype of the offspring.

33
Q

What is phenylketonuria?

A

Recessive genetic condition caused by a mutation in an autosomal gene that codes for the enzymes needed to convert amino acid phenylalanine to the amino acid tyrosine.
People with PKU must restrict the amount of protein they consume, otherwise the phenylalanine levels can become toxic and impair brain development.

34
Q

What is inductive reasoning?

A

Occurs when scientists base a theory on observations of some but not all cases, allowing for the possibility that the conclusion could be false.

35
Q

What is deductive reasoning?

A

Occurs when we apply established knowledge to explain an observation.

36
Q

How can we identify recessive traits in a pedigree chart?

A

If the characteristic is recessive, two parents without the characteristic can have a child with the characteristic.

37
Q

How can we identify dominant traits in a pedigree chart?

A

If the characteristic is dominant, two parents with the characteristic can have a child without the characteristic.

38
Q

Why do many societies prohibit marriage between close relatives based on the pedigree chart analysis?

A
  • Most genetic disorders are rare in the general population, but more common within closely related family groups.
  • Permitting breeding between close relatives would further increase the frequency of people with the genetic disorder.
39
Q

What is incomplete dominance?

A

When a heterozygous will have an intermediate phenotype.

40
Q

What is an example of incomplete dominance inheritance?

A
  • Mirabilis jalapa has multiple pure breeding alleles controlling flower colour through pigment production.
  • In a heterozygous, both of the pigments will be produced and the plant will appear as an intermediate colour.
  • For example, CrCw denotes a plant expressing both the red and white pigment and therefore appears pink.
41
Q

What is codominance?

A

When a heterozygote has a dual phenotype.

42
Q

What is an example of codominance?

A

AB red blood cells will bind to the same antibodies as both type A red blood cells and type B red blood cells.

43
Q

What is a pedigree chart?

A

Shows a record of ancestry and so appears as a family tree with symbols representing individuals phenotype and sex.
- Squares representing males and circles representing females.
- Filled shapes represent the presence of a characteristic and empty shells represent the lack of a characteristic.

44
Q

How could we determine whether a characteristic could be sex linked or is caused by an autosomal gene?

A

1) Determine whether the characteristic is caused by a dominant or recessive allele.
2) Look for one of the following patterns of inheritance that would disprove sex-linked inheritance, and indicate autosomal inheritance.

45
Q

How can we determine whether a characteristic is recessive for determination of sex or autosomal genes for a daughter?

A

If a characteristic is recessive, the daughter must have inherited a recessive allele from both parents. If her father has a dominant phenotype the allele cannot be sex-linked.

46
Q

How can we determine whether a characteristic is recessive for determination of sex or autosomal genes for a son?

A

If the characteristic is dominant, the son must have inherited a dominant allele from his mother (and Y chromosomes from the father). So if his mother has the recessive phenotype, the alleles cannot be sex-linked.

47
Q

What is the relationship between number of alleles for a gene and the phenotypes produced?

A

Although an individual can only have two alleles for each gene, thr populations gene pool may contain alleles for a given gene.
This increases the number of phenotypes in a population, as each allele may be dominant, recessive incompletely dominant or co-dominant to another allele.

48
Q

What is the inheritance of ABO blood groups, and what type of inheritance is shown?

A

ABO blood groups is an example of multiple alleles inheritance and there are 3 alleles:
Ia - produces A-type antigens on the surface of red blood cells.
Ib - produces B-type antigens on the surface of red blood cells.
I - doesn’t produce any antigens on the surface of red blood cells.

49
Q

What are the 6 types of genotype?

A

IaIa / Iai - blood group A
IbIb / Ibi - blood group B
IaIb - blood group AB
ii - blood group O

50
Q

What are the 4 types of phenotype?

A
  • Ia and Ib are dominant to I as there is no difference in phenotype for the homozygous dominant and heterozygous individuals.
  • Ia and Ib are codominant because when they are present together within a heterozygote, both the A antigen and B antigen are expressed om red blood cells, giving a dual phenotype.
51
Q

How is codiminance different to incomplete dominance?

A

How the heterozygous phenotypes manifest differs:
- In codominance, both individual phenotypes (due to each allele can be identified) in what is called a dual phenotype - AB red blood cells nind to the same antibodies as type A and B red blood cells.
In incomplete dominance, an intermediate phenotype is produced due to mixing of the product of each allele:
- Mirabilis jalapa appears pink due to the mixing of the red and white pigments produced by the 2 alleles.

52
Q

How are chromosomes used in sex determination in humans?

A

When meiosis occurs to form sperms either on the X or Y chromosome will be included in each sperm cell. This sex chromosome can then determine whether a zygote develops male or female characteristics.

53
Q

What are the 2 sets of sex chromosomes?

A

The human population has 2 sets of chromosomes: X and Y
XX - female
XY - male

54
Q

What are sex-linked genes?

A

Genes located only on the X chromosome

55
Q

Why is it important to know whether the males gamete contains an X or Y chromosome when predicting inheritance of genes that are located on the C chromosome?

A

Far more genes are carried by the X chromosome than the Y chromosome.

56
Q

What is haemophilia?

A

A disorder in which blood does not clot properly and is an example of a sex-linked genetic disorder, caused by a recessive allele.
There are 2 alleles, which are found on the X chromosome:
XH - no haemophilia
Xh - haemophilia
Y - used to indicate the Y chromosome, which does not have the locus for the haemophilia gene.

biology (28 decks)

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