B5.1 Genes, Inheritance, and Selection Flashcards by Charles Chahine

What is the phenotype?

The appearance of an organism

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What is varition?

Differences within a species

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What are the causes of variation?

The genetic material you inherit from your parents - genetic variation

The environment in which you live - environmental variation

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What are the differences between continuous and discontinuous variation?

Discontinuous = A characteristic that falls into distinct groups. E.g blood type

Continuous variation = A characteristic that can be any value between a minimum and maximum

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What graph would you use for continuous and discontinuous data?

Continuous - Histogram (often the bars are removed and just the line showing the trend is drawn

Discontinuous - Bar chart

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What is a clone?

An organism that is genetically identical to its parent

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What is the difference between sexual and asexual reproduction?

Sexual = requires two parents and causes variation

Asexual = requires one parent and the genes are identical to the offspring

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Give examples of plants and animals that can reproduce asexually?

Potato plants sea anemones

Spider plants Star fish

Daffodils

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What are gametes?

Sex cells such as sperm and ova

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What are the advantages and disadvantages of asexual reproduction?

Advantages:

-if the parent has well adapted genes, its identical set of DNA can be passed on
-Only one parent is needed = reproduction is faster = more offspring

Disadvantages:

-changes to the biotic or abiotic factors may destroy the species.All are affected

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What are the advantages and disadvantages of sexual reproduction?

Advantages:

-Variation in offspring = better adaptations to different environments

Disadvantages:

-Reproduction requires two parents = slower = less offspring produced

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What are diploid cells?

cells that contain two sets of each chromosome.

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What are haploid cells

Cells that contain a single set of chromosomes. E.g sperm and ova

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What is a zygote?

When during fertilisation two haploid gamete cells join together to form a diploid cell (zygote)

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What is a genome?

The entire genetic material of an organism

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How are gametes made?

Gametes are produced by meiosis, resulting in 4 haploid cells being produced from one diploid parent cell.

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What is the first stage of meiosis?

Chromosones are copied
Chromosomes line up along the middle of the cell in pairs
One memeber of each pair is pulled to opposite ends of the cell
Cell divides in 2
Two seperate cells are formed.

What is the second stage of meiosis?

The chromosomes line up along the middle of each of the two new cells
Each chromosome is pulled in half. Single copy of each chromosome goes to opposite ends of the cell.
Each cell then divides into two resulting in 4 haploid cells

How does meiosis create genetic variation?

Meiosis results in cells that are genetically different from each other and from the parent cell, creating genetic variation

What are alleles?

Different forms of a gene

What is the difference between a dominant and recessive allele?

Dominant allele = Alleles that will always show up in an organisms phenotype if they are present in its genetic material

Recssesive = Only expressed in the phenotype only if you have two copies of the allele

What is the genotype?

The combination of alleles present in an organism

What is the difference between homozygous and heterozygous?

Homozygous = Two copies of the same allele

Heterozygous = Two copies of different alleles

What is special about the 23rd pair of chromosomes?

These are the sex chromosomes.
XX = female
Xy = male

How is the sex determined in an offspring?

Male gametes can either have an x or y chromosome, so it is the father that determines the sex of its offspring All female gametes contain an X chromosome

When does a mutation occur?

When the sequence of DNA bases is altered by: -not replicating correctly -benzene and ethanol and ionising radiation (e.g ultraaviolet)

Do mutations affect the organisms phenotype?

Most cases = Does not affect phenotype Some mutations = May influence an organisms phenotype Few mutations = Will determine an organisms phenotype

Why can mutations be harmful?

They can cause cancer (When cells grow and divide uncontrollably) Cause the production of abnormal protein channels that do not function properly like cystic fibrosis Cause different shaped protein molecules to be made. E.g sickle cell anaemia that have unusually shaped haemoglobin molecules = blood cells = sickle shaped = can block blood vessels starving cells of oxygen

When can a mutation be beneficial?

Mutations in some bacteria enable them to be resistant to antibiotics increasing their chance of survival

How can mutations alter an organisms phenotype ? (Higher + separate)

[If a mutation occurs, DNA bases may be changed, added or deleted. This changes the sequence of bases Therefore the order of bases (in mRNA) produced during transcription may one different. ] [The amino acid acids may be assembled in a different order, The wrong protein may be produced, or it may fold incorrectly and form a different shape. ] [If a mutation occurs in the non coding DNA that trigger transcription, the gene may not be transcribed into mRNA. This means the protein the gene codes for will bot be produced.]

What did Gregor Mendel discover? When?

Experimented on peas in 1866 Noticed that characteristics in plants were determined by hereditary units (genes). Hereditary units are passed on from both parents, one unit from each. Hereditary units are dominant or recessive

What did Friedrich Miescher discover? When?

There is an acidic substance present in the nucleus of a cell also known as DNA (1869)

What did Oswald Avery discover? When?

Transferred DNA between bacteria IN 1944 Proved that Genes can be transferred from one generation to the next Showed that genes are made up of DNA

What did Erwin Chargaff discover? When?

Even though different organisms have different amounts of DNA , all DNA contains equal amounts of adenine , thymine, guanine, cytosine (also known as base pairings) 1950

What did Maurice Wilkins and Rosalind Franklin do? When?

Imaged DNA crystals using X-rays in 1952

What did James Watson and Francis Crick do? When?

Published their description of DNA, describing it as a double helix in 1953

What happened between 1953 - 2000 in terms of genetic discoveries?

Scientists identified individual genes that code for genetically inherited disorders such as cystic fibrosis. Genetic engineering also developed

What is genetic engineering?

Altering an organisms characteristics by adding genetic material.

What project was created in 2003? What did it do?

Human genome project: Scientist working across the globe identified and sequenced around 24 000 genes - the complete set of genes in the human body

What is gene therapy?

When scientists try to replace faulty (mutated) genes with normal copies of the gene This might be able to cure genetic diseases, such as cystic fibrosis