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Biology - Real One > B5.1 Inheritance > Flashcards

B5.1 Inheritance Flashcards

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1
Q

What is meant by variation

A

Differences within a species

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2
Q

What is meant by phenotype

A

Characteristics which are observed in an organism

The appearance of an organism is called its phenotype

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3
Q

What are two causes of variation and what is meant by them

A

Genetic variation (variation caused by genetic material present in an organism that is inherited from their parents )

Environmental variation (variation caused by the environment in which you live)

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4
Q

What are examples of genetic variation

A
  • eye colour
  • blood group
  • presence of a genetic disorder
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5
Q

What are examples of environmental variation

A
  • language they speak
  • where they live
  • weight
  • Learning
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6
Q

What is discontinuous variation

A
  • characteristics which fall into distinct groups
  • can only take results I’m specific (discrete) values
  • displays genetic variation
  • displayed as a bar chart

Examples:

  • gender
  • eye colour
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7
Q

What is continuous variation

A
  • variation which can take any value between a minimum and a maximum
  • can take any value within a range
  • shows genetic and environmental variation
  • displayed as a histogram ( with bars removed only line showing the trend)

Examples:

  • leaf SA
  • skin colour
  • length of fur
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8
Q

What are diploid cells

A

Cells which contain two sets of chromosomes

There are 46 chromosomes in total

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9
Q

What are haploid cells

A

They have one of each chromosome

They only contain 23 chromosomes

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10
Q

What is a zygote

A

A fertilised egg

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11
Q

What happens during fertilisation

A

Two haploid gametes join together

This forms a diploid cell known as a zygote

The zygote divides many times by mitosis to produce a new organism

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12
Q

What is a genome

A

All of the genetic material present in an organism

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13
Q

Why are the combination of genes that an organism display unique

A

It is a mixture of both parents genetic material

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14
Q

How are gametes made

A

Meiosis - cell division which produces gametes

  • 4 haploid cells are made from one diploid parent cell
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15
Q

What happens during meiosis

A

There are two main stages:

In the first stage :
1) chromosomes are copied

2) Chromosomes line up in the middle of the cells in pairs (1 from mother and 1 from father)
3) one member of each pair is pulled to opposite ends of the cell
4) the cell divides in two
5) two separate cells are formed

Stage 2:

6) chromosomes line up in the middle of the two new cells
7) each chromosome is pulled in half. A single copy of each chromosome is pulled to opposite ends of the cell
8) each cell divides in two, resulting in 4 haploid cells

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16
Q

What are alleles

A

Different versions of the same gene

17
Q

What is a dominant allele?

A

Version of a gene whose characteristics is always expressed if present in the genotype

Only one dominant allele is needed for characteristics to be expressed

Shown by a capital letter

18
Q

What is a recessive allele?

A

A version of a gene whose characteristics are only expressed if two copies are present in the genotype

Two recessive alleles are needed for the characteristic to be expressed

Shown by a lowercase letter

19
Q

What is a genotype

A

The combinations of alleles present in an organism

20
Q

What are the three main types of genotypes

A

Homozygous dominant - two copies of the same allele that are dominant (e.g BB)

Homozygous recessive - two copies of the same allele that are recessive (e.g bb)

Heterozygous - different alleles of a gene (e.g Bb)

21
Q

What is a genetic cross

A

A technique used to show the possible characteristics of an offspring

22
Q

What is a punnet square?

A

A diagram used to show the possible genetic makeup of offspring based on a mother and fathers genes

23
Q

How are male chromosomes different to female chromosomes

A

The 23 pair of chromosomes is different depending on whether you are male or female

Female chromosomes have two large XX

Male chromosomes have one large C and one smaller Y chromosome

24
Q

What is a mutation?

A

A change in the sequence of DNA bases

This can occur if DNA doesn’t replicate correctly

25
Q

Why are some mutations harmful

A

They can cause cancer (cells grow and divide uncontrollably)

They can cause the production of abnormal protein channels (channels that allow molecules to be transported through cell membranes won’t function properly)

They can cause different shaped protein molecules to be made

26
Q

Are all mutations harmful?

A

Some are neutral - they don’t benefit or harm you.

Some mutations can be beneficial - e,g mutations in some bacteria allow them to be resistant to antibiotics

27
Q

How can mutations alter an organisms phenotype

A

If a mutation occurs in a gene, DNA bases can be changed, added or deleted changing the sequence of bases so the wrong protein will be produced

28
Q

The history of genetics - how has the understanding of genetics changed over time? (1886-1950)

A

1886 : DISCOVERY THAT CERTAIN CHARACTERISTICS ARE INHERITED

  • Mendel observed that characteristics are passed on from parents to offspring
  • characteristics in plants were determined by hereditary units
  • hereditary units are passed on from both parents
  • hereditary units are dominant or recessive

1869: NUCLEIN DISCOVERED
Miescher discovered that there is an acidic substance present in the nucleus of a cell

1944 : GENES CAN BE TRANSFERRED FROM ONE GENERATION TO THE NEXT
- Avery transferred DNA between bacteria. This showed genes are made up of DNA

1950 - DNA BASE PAIRS DISCOVERED
- chargaff found that all DNA contains equal quantities of adenine and thymine and cytosine and guanine

29
Q

how has the understanding of genetics changed over time? (1952-2003)

A

1952 - DNA CRYSTALS PHOTOGRAPHED
- Wilkins and Franklin imaged DNA crystals using X -Rays

1953: DOUBLE HELIX STRUCTURE OF DNA
- Watson and Crick published their description of DNA, describing it as a double helix held together by complementary base pairs

1953-2000 ADVANCES IN GENETICS
Scientists identified individual genes that code for inherited diseases

2003 HUMAN GENOME PROJECT COMPLETED:
- Scientists around the world identified 24000 genes which is the complete set of genes in the human body

Biology - Real One (10 decks)

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