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Flashcards in Inheritance Deck (27)
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Define inheritance

the transmission of genetic information from generation to generation


Define chromosomes

a thread of DNA, made up of a string of genes


Define genes

a length of DNA that is the unit of heredity and codes for a specific protein


Define allele

any of two or more alternative forms of a gene


Define haploid nucleus

a nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg)


Define diploid nucleus

a nucleus containing two sets of chromosomes (e.g. in body cells)


Describe the inheritance of sex in humans (XX
and XY chromosomes)

- Egg: X chromosome
- Men: X or Y chromosome
- XX = girl, XY = boy => 50%


Define mitosis

- nuclear division giving rise to genetically identical cells in which the chromosome number is maintained
- roles: growth, repair of damaged tissues, replacement of worn out cells and asexual reproduction


Define meiosis

- reduction division in which the chromosome number is halved from diploid to haploid
- gametes are result. results in variation


Define genotype

genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG)


Define phenotype

physical or other features of an organism due to both its genotype and its environment


Define homozygous

having two identical alleles of a particular gene .Two
identical homozygous individuals that breed together will be pure-breeding


Define heterozygous

having two different alleles of a particular gene


Define dominant and recessive

- an allele that is expressed if it is
- an allele that is only expressed
when there is no dominant allele of the gene


Define continuous variation

influenced by genes and environment, resulting in a range of phenotypes between two extremes


Define discontinuous variation

caused by genes alone and results in a limited number of distinct phenotypes with no intermediates


Define mutation

- a change in a gene or chromosome => leads to variation
- cause: damage to DNA or failure in the copying process that occurs before nuclear division


Down syndrome

- Cause: Trisomy 21 (3 copies of chromosomes 21) when there's a fault in meiosis


Describe sickle cell anaemia, and explain its
incidence in relation to that of malaria

- An inherited disease
- The gene for haemoglobin exists in 2 forms: HbN and HbS.
- HbSHbS = people who have the disease and experience fatigue and pains in joints
- RBC are misshaped => not as flexible and will block up blood vessels => cannot get oxygen
- Relation to malaria:
+ Protect against malaria
+ Natural selection


Outline the effects of ionising radiation and
chemicals on the rate of mutation

Rate is increased. Ultra violet radiation, X-rays and gamma rays are the most damaging


Explain codominance by reference to the inheritance of ABO blood groups – phenotypes, A, B, AB and O blood groups and genotypes IA , IB , and IO

- IA and IB are codominance
- IO is recessive to both
- When codominance => both alleles are expresses in the phenotype


Define natural selection

The greater chance of passing on of genes by the best adapted organisms


Importance of natural selection as a possible mechanism for evolution

Competition for resources => only those with advantageous phenotypes are more likely to feed/survive => stay alive => breed and pass on genes => evolution


Describe the development of strains of antibiotic resistant bacteria as an example of natural selection

- Bacteria exposed to an antibiotic most are killed. Some are resistant due to mutation => survive => reproduce and pass on genes for offsprings


Describe the role of artificial selection in the production of varieties of animals and plants

- Humans choose a feature of animal/plant to improve
- Animals/plant showing these features are bred to produce the next generation
- Process = selective breeding
=> economy improved


Define genetic engineering

taking a gene from one species and putting it into another species


Explain why, and outline how, human insulin
genes were put into bacteria using genetic engineering

- Safer to use human insulin because less risk of rejection, more cost-effective, and less risks of diseases from animals
- The gene that codes for production of insulin is identified and remove it from the rest of the DNA using endonuclease enzyme
- Plasmid (a circular piece of DNA) is removed from a bacterium
- The endonuclease opens the plasmid
- The human insulin making gene is put into the plasmid using ligase
- The plasmid is placed back into the bacterium => asexual reproduction