B5 Flashcards
What are mutations? How do they form?
Mutations occur when a sequence of DNA is altered. They are a difference in usual sequences of DNA strands.
Suggest why sunbathing increases your chance of mutations occurring in your DNA.
Ultraviolet light, a form of ionising radiation, can trigger the formation of mutations in DNA.
Name three diseases caused by genetic mutations.
Cystic fibrosis, sickle cell anemia, and phenylketonuria.
Explain why radiographer leave the room when taking an x-ray of a patient.
X-rays are a form of electromagnetic waves; being exposed to these waves frequently to take x-rays of multiple patients can cause mutations in the DNA that could be potentially harmful.
Define phenotype.
The visible characteristics of an organism as determined by its combination of alleles.
Define genotype.
The combination of alleles present in an organism.
Explain how a genetic mutation could lead to an enzyme being inactive.
1 - mutations occur because of a change in a DNA sequence.
2 - a change in a DNA sequence will mean different bases will be transcribed onto the mRNA strand during transcription.
3 - these bases will translate to different amino acids. Their different order determines which proteins are produced and how.
4 - if the protein is an enzyme, then it could be altered by the new order of amino acids - its active site could change in shape.
5 - the enzyme would no longer be complementary to its substrate, preventing it from bonding to it and catalysing a specific reaction.
6- this makes it inactive.
Explain how some proteins may not be produced at all due to mutations.
1 - mutations occur due to DNA bases being altered. Bases may be removed, added or changed.
2 - if the mutation occurs in the non-coding DNA, then this will mean that the coding DNA will not be activated/will not function properly.
3 - This means that transcription will either not take place at all or will not take place properly.
4 - meaning that transcription will not take place, meaning no amino acids will be produced, and thus no protein will be produced.
What is a protein channel?
A channel that allows molecules to pass through the cell membrane.
Define the genome.
All of the genetic material present in an organism.
What is evolution?
The change in inherited characteristics in a population over time, through the process of natural selection.
Explain the process of natural selection.
Some genetic variants give rise to characteristics (phenotypes) that are well suited to an environment. Members of a species with advantageous phenotypes are more likely to survive and pass down these characteristics to their offspring. Meanwhile, members without this phenotype are less likely to survive and reproduce and thus less likely to pass down their non-advantageous characteristic to their offspring, leading to the entire species gradually all gaining that advantageous phenotype as those without it die out.
Define a gene.
A section of DNA that codes for a specific characteristic.
What are the examples of sex cells in animals?
Ovum and sperm.
What is a gamete?
A sex cell.
What is a zygote?
A fertilised egg cell.
Define chromosomes.
DNA structures that carry genetic information in the form of genes.
What is continuous variation?
Variation that has many small degrees of difference and can be put on a scale; often has a minimum and a maximum. E.g. height.
What is discontinuous variation?
Variation that can be put into set categories, e.g. Blood type.
What is environmental variation caused by?
Factors of the environment the organism lives in.
What is genetic variation caused by?
The combination of genes the organism inherited from its parent(s).
State the difference between heterozygous organisms and homozygous organisms.
Heterozygous organisms receive different copies of each allele. Homozygous individuals receive two copies of the same allele.
What is coding DNA?
Coding DNA refers to the genes that provid the instructions required to synthesise proteins.
Why are only a small proportion of genes in the genome expressed?
To be expressed, genes must first be activated.
What is non-coding DNA?
It causes the activation or deactivation of the coding genes.
What is evolution?
The gradually change in a species over time.
Define a gene.
A section of DNA that codes for a certain characteristic.
Define an allele.
Different versions of the same gene.
