3 1 reproduction

Asexual reproduction is a reproductive process that only involves one parent and that results in genetically identical offspring.

Advantages of asexual reproduction include:

False. Asexual reproduction results in offspring that are genetically identical to their parents.

The main disadvantage of asexual reproduction is that offspring are genetically identical. A population of genetically identical individuals are less likely to be able to adapt to changes in the environment.

Sexual reproduction is a reproductive process that involves the fusion of gametes from two parents and that produces genetically varied offspring.

Sexual reproduction results in genetically varied/different offspring, meaning that a population is more likely to be able to adapt/respond to changes in the environment. Energy requirements are higher, however, due to the need to find a mate‎.

Meiosis is a type of nuclear division that produces genetically different cells. The cells produced by meiosis are gametes (sex cells).

The role of meiosis is to produce genetically varied gametes (sex cells) with half the normal chromosome number.

False. Meiosis results in genetically different cells.

During meiosis the chromosome number is halved from diploid (46 in humans) to haploid (23 in humans). For this reason meiosis is known as reduction division.

The daughter cells produced by meiosis can be described as follows:

Meiosis is crucial because it ensures that gametes (sperm and egg cells) have half the chromosome number, allowing for the correct chromosome number after fertilisation.

Meiosis produces four daughter cells.

Some key differences between meiosis and mitosis include:

DNA is a polymer that consists of two strands coiled around each other to form a double helix. The strands are held together by a series of paired bases.

False. The DNA base pairs are held together by weak hydrogen bonds.

The molecule shown is a nucleotide.

A polymer is a large molecule made up of many repeating subunits. DNA is a polymer containing many repeating nucleotides.

The four nucleotide bases in DNA are:

Bases in DNA pair together via complementary base pairing:

False. A pairs with T in DNA base pairing.

The genome is all of the DNA that an organism has.

A gene is a section of DNA which codes for a specific protein.

Extracting DNA from strawberries involves the following steps beyond steps 1 and 2:

Genes code for proteins as follows:

False. Each type of protein folds into a different specific shape.

True. Enzymes are proteins which fold to produce an active site with a structure that is complementary to a specific substrate.

Protein synthesis is the process by which proteins are made in a cell.

The two processes that occur during protein synthesis are:

During transcription an mRNA strand that is complementary to the coding DNA of a gene is produced.

The role of RNA polymerase in transcription is to:

False. Translation occurs on ribosomes in the cytoplasm. Transcription occurs in the nucleus.

Translation can be described as follows:

A codon is a triplet of mRNA bases that corresponds to a specific amino acid.

The role of tRNA is to transfer specific amino acids to the ribosome. The amino acid transferred is determined by the region of the tRNA called the anticodon, which binds to a complementary mRNA codon.

False. During translation the amino acids are linked to form polypeptides.

A genetic variant is a change in the normal base sequence of DNA. Variants arise due to mutation.

Non-coding DNA is DNA that is not part of a gene, so does not code for protein.

True. Changes to non-coding DNA can affect phenotype. Even though non-coding DNA does not code for proteins, changes in these regions can influence the transcription of coding DNA.

Genetic variants in the non-coding DNA at the start of a gene can influence the binding of RNA polymerase; this may increase or decrease transcription of the gene, altering the quantity of protein synthesised.

Genetic variants in non-coding DNA can affect phenotype as follows: