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76 Cards in this Set

  • Front
  • Back


Differences between individuals of the same species

How can variation occur?



Genetic factor example?


Environmental factor example?



Molecules that code for genetic information and make up chromosomes


Small section of DNA of a chromosome that determines a particular characteristic

Order cell, chromosomes, DNA, genes and nucleus biggest to smallest?







What do genes carry?

Information for you to develop

What do different genes control?

Different characteristics


A long molecule found in the nucleus of all cells containing DNA


Control centre of a cell and contains DNA

Where are genes found?

In sections of DNA

In chromosomes which are located inside the nucleus of every cell

What are chromosomes made of?

DNA molecules

What are DNA molecules made up of?

Two very long strands which coil to form a double helix

What do DNA molecules complete a full set of instructions for?

How the organism should be constructed

How each cell should function

How do genes control the development of different characteristics?

Genes issue instructions to the cell

The cell carries out instructions by producing proteins


Long organic compounds made of amino acids

What can proteins formed inside a cell be?



What are structural proteins for?

Cell growth


Structural protein example?


What are functional proteins for?

Speed up chemical reactions

Functional protein example


What do chromosomes normally come in?


What do both chromosomes in a pair have?

Same sequence of genes

How many chromosome pairs do human cells have?

23 pairs

How many individual chromosomes do human cells have?


What is different bout the chromosomes in sex cells?

They have single chromosomes= 23 individual chromosomes


An alternative form of a particular gene

What do you inherit for each gene?

One allele from father and one from mother


Inheriting two alleles that are the same


Inheriting two alleles that are different

Why do siblings look different?

They randomly inherit different combinations of alleles


The genetic make-up of an organsism


The characteristics shown by an individual

Dominant allele?

Controls the development of a characteristic even if it's present on only one chromosome in a pair

Recessive allele?

Controls the development of a characteristic only if a dominant allele isn't present

If the recessive allele is present on both chromosomes in a pair

How many sex chromosomes are there in a human body cell?

One of the 23 pairs

What gene determines the sex on the Y chromosome?

Sex-determining region Y gene

What happens if the sex-determining region Y gene isn't present?

They embryo will develop into a female

What happens if the sex-determining region Y gene is present?

Testes begin to develop

What do testes produce six weeks after fertilisation?

A hormone called androgen

What happens after androgen is produced?

Specialised receptors detect the androgen

Male reproductive organs begin to grow

What happens if the Y chromosome is present but androgen isn't detected?

The embryo develops female sex organs apart from the uterus

The baby has a female body but is infertile

What is Huntington's disease caused by?

A dominant allele

Heterozygous and homozygous alleles

What is Cystic Fibrosis caused by?

Recessive allele

Homozygous allele

What if a person possesses one allele for Cystic Fibrosis?

They are a carrier

Heterozygous allele

What are the implications if an adult is genetically tested and the result is positive?

Decide not to have children

Adopt children

Have children but to accept that they may also inherit disorder

Why are children tested to see if they have disease-causing genes?

To take preventative measures before prescribing certain drugs that may have a negative effect due to the genetic make-up

Susceptibility of certain diseases

Tailor healthcare

To stop genetic disorders from being passed on, eliminating them

How are fetuses tested?


Chorionic villus test

How does amniocentesis occur?

Fluid surrounding the fetus/placenta is injected out

This can be tested for faulty alleles

How does the chorionic villus test occur?

Suction tube removes cells from chorionic villi

What are the risks of testing fetuses?


False negative/positive as it is not 100% reliable

What are the implications if a fetus was tested and the result was positive?


Give birth and take care of child

Tell family members they too may carry the faulty allele

What are ethical concerns about testing fetuses?


The effects the information may have on an individual and relationships

Not right to interfere with nature

Who has the right to decide if a disorder is worth living with

Confidentiality- employers/insurance companies causes discrimination

What are the outcomes of a false positive?

Termination when there is no disorder

What are the outcomes of a false negative?

Parents not prepared when child is born with a disorder

What are the benefits of embryo selection?

Prevents babies from having genetic disorders

How can embryos be produced?


What is done alongside IVF to check for a specific genetic disorder?

Pr-implantation Genetic Diagnosis

IVF and PGD steps?

Ova harvested


Embryos divide into eight cell stage

Single cell removed from each embryo

Cells tested to see if they carry the alleles for a specific genetic disorder

Healthy embryos implanted into uterus

What are the ethical problems of embryo selection?


Pre-selection-reduces variation

Asexual reproduction?

New offspring are reproduced that are identical to the parent

What organisms do asexual reproduction?

Single-cell e.g. bacteria/plants

How do single-cell organisms reproduce?

Divide to form two new individuals

What are the new individuals?



An organism genetically identical to the parent

What is variation like in asexually produced organisms?

No genetic variation

Only environmental variation

How can animal clones occur naturally?

Identical twins- the cells of an embryo separate

How can animal clones be produced artificially?

Nucleus removed from an adult body cell

Transferred into an empty unfertilised egg cell

New individual will have exactly the same genetic information as the donor

How do plants naturally produce clones?

With bulbs and runners

Bulb example?


Runner example?

Strawberry plants

What is the problem with asexually produced organisms?

No genetic variation

Susceptible to the same diseases as the parent plant

Stem cells?

A cell of a human embryo or adult bone marrow that has the ability to differentiate

Specialised cell?

It has a certain function

What can stem cells be used for?

Replace damaged tissues- Parkinson's disease/heart disease/other organ diseases

Red blood cells- leukemia

Insulin- diabetes