B11 - Inheritance Flashcards
Define inheritance.
the transmission of genetic information from generation to generation.
Define chromosome.
a thread-like structure of DNA, carrying genetic information in the form of genes.
Define gene.
a length of DNA that codes for a protein.
Define allele.
a version of a gene.
Define haploid nucleus.
a nucleus containing a single set of unpaired chromosomes.
Define diploid nucleus.
a nucleus containing two sets of chromosomes.
Define mitosis.
nuclear division giving rise to genetically identical cells.
Define meiosis.
reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells.
Define genotype.
the genetic make-up of an organism in terms of the alleles present.
Define phenotype.
the observable features of an organism.
Define homozygous.
having two identical alleles of a particular gene.
Define heterozygous.
having two different alleles of a particular gene.
Define dominant.
an allele that is expressed if it is present.
Define recessive.
an allele that is only expressed when there is no dominant allele of the gene present.
Define variation.
differences between individuals of the same species.
Define mutation.
a change in a gene or chromosome.
What are examples of cells with haploid nuclei?
gametes / sperm / egg / pollen / ovule
What are examples of cells with diploid nuclei?
all body cells
How many pairs of chromosomes are in human diploid cells?
23
What is the 23rd pair of chromosomes called?
the sex chromosome
What is the chromosome pair for males and females?
male - XY
female - XX
Where is DNA found?
the nucleus of cells.
What is made of DNA?
genes.
Why is DNA essential for life?
genes determine all our features and cell activity.
What four bases make up DNA?
adenine, thymine, cytosine, and guanine.
Which bases join?
adenine and thymine
guanine and cytosine
Why is the replication of DNA so important?
Enables cell division, mitosis, and produces sex cells.
Describe how DNA replicates.
A section of DNA ‘unzips’ and separates the bases, spare bases latch on so there are no two identical sections of DNA.
What happens to the chromosome number at fertilisation?
it is restored/doubled.
How many cells does mitosis produce?
2
What is the role of mitosis?
growth, cell replacement during development, in the repair of damaged tissues, and asexual reproduction.
What are stem cells?
unspecialised cells.
What is the role of meiosis?
make haploid gametes, to produce genetic variation.
What is genetic variation?
the differences in genotype.
What is phenotypic variation?
the differences in phenotype.
What is continous variation?
when the individuals in a population have a range of phenotypes which vary between two extremes.
What is discontinuos variation?
when there are two or more disctinct categories. each individual falls into only one of these categories, so there is a limited number of phenotypes.
What is natural selection?
the increased chance of passing on alleles by the best-adapted organisms.
What are the five stages of natural selection?
Genetic variation
Overproduction
Struggle for existence
Survival of the fittest
Advantageous characteristics passed on to the offspring
Define adaptation.
the process, resulting from natural selection, by which populations become more suited to their environment over many generations.
