B13 - Reproduction

What is sexual reproduction?

Sexual reproduction involves the joining (fusion) of female and male gametes formed by Meiosis. Meiosis leads to the formation of non-identical cells, sperm and egg cells in animals and pollen and egg cells in flowering plants. There is a mixing of genetic information that leads to variation in the offspring.

What is asexual reproduction?

In asexual reproduction, there is no fusion of gametes and only one parent. There is no mixing of genetic information, leading to genetically identical offspring (clones).

Only mitosis is involved with which type of reproduction?

Asexual reproduction

How do cells in the reproductive organs divide?

By meiosis to form the gametes(sex cells)

What is a difference between body cells and gametes?

Body cells have two sets of chromosomes whilst gametes only have one.

What happens in meiosis?

In meiosis, the genetic material is copied and the cell divides twice to form four gametes, each with a singles set of chromosomes. All gametes are genetically different to each other.

In what process do gametes join up together?

Gametes join in fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis. The number of cells increase and the embryo develops with cells differentiating.

How does sexual reproduction improve survival?

Sexual reproduction produces variation that helps survival through natural selection if the environment changes. Natural selection is sped up by humans through selective breeding.

Why is asexual reproduction better than sexual reproduction?

Asexual reproduction only needs one parent , is time and energy efficient, often faster than sexual reproduction, and many identical offspring is produced when conditions are favourable.

How does malaria parasites reproduce?

Sexually in mosquitos and asexually in their human host.

What can fungi do when reproducing?

Many fungi reproduce asexually by spores but sexually to produce variation.

What can plants do when reproducing?

Many plants produce seeds sexually but also reproduce asexually, for example by runners or bulb division.

What is the genome of an organism?

The genome of an organism is the entire genetic material of that organism

Has the whole human genome been studied?

Yes, this is important for medicine in the future.

What is the genetic material in a nucleus composed of?

DNA. DNA is a polymer made up of two strands forming a double helix

What is a gene?

A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.

What is the structure of DNA?

The long strands of DNA consists of alternating sugar and phosphate sections. Attached to each sugar is one of four bases - A,C,G or T. Each unit of a sugar , phosphate or base is called a nucleotide.

What is the code for a particular amino acid?

A sequence of three bases

What does the order of the bases in a DNA strand control?

The order of bases controls the order in which amino acids are assembled to produce a particular protein.

What bases are always linked in the complementary strands of DNA?

c-g

t-a

What happens if the protein chain is complete?

It folds up to form a unique shape which enables the protein to carry out its function in the cell.

What does non coding parts of DNA do?

Non coding parts switch genes on and off, so variations in these areas of DNA can affect how DNA can be expressed.

What can a change in the DNA structure result in?

A change in the protein synthesized by the gene

Does mutations alter the protein?

Mutations occur continuously. Most do not alter the protein, or they alter it so slightly that the function is not affected.

What can a few mutations do to a protein?

A few mutations code for an altered protein with a different shape affecting its function. This may be an advantage or disadvantage.

What are characteristics controlled by?

Some characteristics are controlled by a single gene. Each gene may have different forms called alleles

what does phenotype and genotype mean

genotype - the collection of genes an organisms has

Phenotype - the physical characteristics of an organism

What happens if two alleles are the same?

The individual is homozygous for that trait but if the alleles are different they are heterozygous

What is a difference between a dominant and a recessive allele?

A dominant allele is always expressed in the phenotype even if only one copy is present . A recessive allele is only expressed if two copies are present.

What are most characteristics a result of?

Multiple genes interacting, rather than a single gene.

What can a Punnett square diagram predict?

The outcome of a monohybrid cross

How many pairs of chromosomes does ordinary human body cells contain?

23 pairs of chromosomes with 22 controlling general body characteristics only

What is a difference between the sex chromosomes?

In human females the sex chromosomes are the same (XX) whilst the male sex chromosomes are different (XY).

What is Polydactyly?

polydactyl is a dominant phenotype caused by a dominant allele which can be inherited from either or both parent

What is cystic fibrosis?

A recessive phenotype and is caused by recessive alleles which must be inherited from both parents.

what can cells from embryos and fetuses be screened for?

The alleles that cause many genetic disorders

what are embryo and fetal cells used for?

Identifying genetic disorders but screening raises economic, social and ethical issues.

What are the four types of bases in DNA

Adenine

Thymine

Cytosine

Guanine