the whole of GCSE edexcel biology!!!

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Why is one parent an advantage in asexual reproduction?

Can reproduce when conditions are favourable without having to find a mate

Why is the rapid reproductive cycle an advantage in asexual reproduction?

Can produce lots of offspring quickly

What is a disadvantage to asexual reproduction?

No genetic variation between offspring in population

Why is a lack of genetic variation a disadvantage?

Whole population is affected by unfavourable conditions if environment changes

Why is genetic variation an advantage in sexual reproduction?

Some individuals are more likely to survive a change in environmental conditions

Why is genetic variation beneficial over time?

Can lead to natural selection and evolution

Why are two parents a disadvantage in sexual reproduction?

Difficult to find a mate if individuals are isolated

How many daughter cells does meiosis produce?

4

How many chromosomes do the daughter cells in meiosis have?

Half the number of chromosomes

What does meiosis produce?

Genetically different haploid gametes

What is the shape of DNA?

Two strands coiled to form a double helix

What are the DNA strands linked by?

A series of complementary base pairs joined by weak hydrogen bonds

What do nucleotides consist of?

A sugar, phosphate group and one of 4 different bases

What is DNA described as?

A polymer

What is DNA made up of?

Nucleotides

What is a genome?

The entire DNA of an organism

What is a gene?

A section of a DNA molecule that codes for a specific protein

What are three bases in a gene called?

Codon

How do amino acids make a specific protein?

Amino acids in a certain order fold to produce specifically shaped proteins

What is the first part of protein synthesis?

Transcription

What is the second part of protein synthesis?

Translation

What is the first step of transcription?

RNA polymerase binds to a region of non-coding DNA in front of a gene

What happens after the enzyme binds to DNA in transcription?

The two DNA strands unzip

What happens after attaching to ribosome?

For each codon, the ribosome lines up one complementary tRNA molecule

What happens after lining up each codon to tRNA?

Each tRNA molecule carries specific amino acids to ribosome

What happens after amino acids are brought to ribosome?

They join up to form a polypeptide which folds into a specific protein

What is a genetic variant?

A random change in the sequence of bases in DNA

What did Mendel study?

Inheritance in pea plants which he cross-bred

Why are there differences in inherited characteristics?

The offspring inherits 2 different alleles for the same protein

What is a chromosome?

Long coiled up molecules of DNA

What is an allele?

Different version of the same gene

What is a dominant allele?

Only one allele is required for it to be expressed

What is a recessive allele?

Two copies are required for it to be expressed

What is homozygous?

Both alleles in the genotype are the same

What is heterozygous?

The alleles in the genotype are different

What is the genotype?

The combination of alleles an individual has

What is a phenotype?

The physical characteristic expressed

What is a gamete?

A haploid sex cell

What is a zygote?

Diploid cell formed from fusion of two haploid gametes

What is monohybrid inheritance?

The inheritance of a single characteristic

How is the sex of an offspring determined?

The combination of sex alleles

What is codominance?

When both alleles are dominant and affect the phenotype

What are most features of a phenotype a result of?

Multiple genes rather than single gene inheritance

What are the causes of variation?

Genetic and environmental

What is usually within a population of a species regarding genetic variation?

Extensive genetic variation that arise through mutations

What is the effect of most genetic mutations on the phenotype?

No effect

What is the effect of some genetic mutations on the phenotype?

A small effect

What is the rare effect of a genetic mutation on the phenotype?

That a single mutation will significantly affect the phenotype

What are eukaryotic cells?

Cells that have a nucleus and other membrane-bound organelles

What cells are eukaryotic?

Animal and plant

What are prokaryotic cells?

Small simple cells without a nucleus and membrane-bound organelles

What cells are prokaryotic?

Bacteria

What is the function of the nucleus?

Contains genetic material which controls cell's activities

What is the function of the cytoplasm?

Site of most chemical reactions and holds organelles

What is the function of the cell membrane?

Holds the cell together and controls what goes in and out

What is the function of the mitochondria?

Releases energy through aerobic respiration

What is the function of the ribosome?

Site of protein synthesis

What is the function of the cell wall?

To support and strengthen the cell

Where is the cell wall on a diagram?

On the outside

What is the function of the vacuole?

Maintains internal pressure to support the cell

What is the function of the chloroplasts?

Site of photosynthesis

What additional organelles does a bacterial cell have regarding genetic material?

Chromosomal and Plasmid DNA

What is chromosomal DNA?

A long circular chromosome which controls the cell's activities and replication

Where is chromosomal DNA in a bacterial cell?

Floats free in the cytoplasm

What is the function of an egg cell?

To carry female DNA and nourish the developing embryo in early stages

What does the cytoplasm of an egg cell contain?

Nutrients to nourish the developing embryo

What nucleus does the egg cell have?

Haploid

What does the membrane of the egg cell do after fertilisation?

Hardens to stop any more sperm from getting in

Why must the egg cell prevent any more sperm from entering after fertilisation?

To ensure the offspring ends up with the correct amount of DNA

What is the function of the sperm?

To transport the male's DNA to the female's egg

What is the function of the sperm's tail?

Allows it to swim to the egg

Why does the sperm have lots of mitochondria in the middle section?

To release energy through respiration needed to swim distance to egg

What is the function of the acrosome on the front of the sperm's head?

Stores digestive enzymes to break down the membrane of the egg cell

What nucleus does the sperm cell have?

Haploid

Why are the nuclei of the egg and sperm cell haploid?

To produce a diploid offspring with 2 sets of chromosomes at fertilisation

What are cilia?

Hair-like structures

What is the function of ciliated epithelial cells?

To move substances along the surface of the tissue

How do ciliated epithelial cells move substances?

Cilia beat to move them in one direction

Why do lots of ciliated epithelial cells line the airways?

To move mucus up to the throat to be swallowed and not reach lungs

What do microscopes do?

Magnify images and increase the resolution of them

What is resolution?

How well you can distinguish between two points that are close together

What does a higher resolution mean?

Image is clearer and more detailed

How do light microscopes work?

By passing light through the specimen

What can be seen using a light microscope?

Nuclei, chloroplasts and living cells

How do electron microscopes work?

Use electron beam instead of light

Why are electron microscopes better than light?

Higher magnification and resolution

What can you see with an electron microscope?

Smaller things in more detail like the internal structure of mitochondria and chloroplasts

What have electron microscopes allowed?

A greater understanding of how cells work and the role of subcellular structures

What can electron microscopes not see?

Living cells

What order of magnitude is -milli?

10-3

What order of magnitude is -micro (µ)?

10-6

What order of magnitude is -nano?

10-9

What order of magnitude is -pico?

10-12

How do you find the field of view on a microscope?

Use a clear ruler on the stage to measure diameter of circular area visible

How do you calculate magnification?

[\frac{ \text{Image size} }{ \text{Actual size} }]

What do enzymes allow?

For chemical reactions to happen at lower temperatures

What is the active site of an enzyme?

Where it binds to the substrate

What is an enzyme described as having for a substrate?

High specificity

What is the lock and key mechanism?

Complementary substrate fits into the enzyme like a key fits into a lock

What affects rate of reaction of enzymes?

Temperature, pH, and substrate concentration