Chapter 17: Inheritance Flashcards
What are chromosomes made out of
chromosomes are made of DNA, which contains genetic information in the form of genes
Define a gene
a length of DNA that codes for a protein
Define an allele
as an alternative form of a gene
Describe the inheritance of sex in humans with reference to X and Y chromosomes
XY in males and XX in females
What is the use of sequence of bases in a gene
the sequence of bases in a gene determines the sequence of amino acids used to make a specific protein
Why is the sequence of amino acid important
different sequences of amino acids give different shapes to protein molecules
How does DNA control cell function
DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters
How is protein made
• the gene coding for the protein remains in the nucleus
• messenger RNA (mRNA) is a copy of a gene
• mRNA molecules are made in the nucleus
and move to the cytoplasm
• the mRNA passes through ribosomes
• the ribosome assembles amino acids into protein molecules
• the specific sequence of amino acids is determined by the sequence of bases in the mRNA
Why aren’t all genes expressed
cells in an organism contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs
Describe a haploid nucleus
a nucleus containing a single set of chromosomes
Describe a diploid nucleus
a nucleus containing two sets of chromosomes
Describe mitosis
nuclear division giving rise to genetically identical cells
State the role of mitosis
- Growth
- Repairing damaged tissues
- Replacing cells that wear out
- Producing new organisms by asexual reproduction
What happens before mitosis
the exact replication of chromosomes occurs before mitosis
What happens during mitosis
the copies of chromosomes separate, maintaining the chromosome number in each daughter cell
Describe stem cells
unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions
When is meiosis involved
in the production of gametes
Describe meiosis
a reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells
Describe inheritance
the transmission of genetic information from generation to generation
Describe genotype
the genetic make-up of an organism and in terms of the alleles present
Describe phenotype
the observable features of an organism
Describe homozygous
having two identical alleles of a particular gene
When does pure breading occur
two identical homozygous individuals that breed together will be pure-breeding
Describe heterozygous as
having two different alleles of a particular gene
Will heterozygous be pure breeding
a heterozygous individual will not be pure-breeding
Describe a dominant allele as
an allele that is expressed if it is present in the genotype
Describe a recessive allele as
an allele that is only expressed when there is no dominant allele of the gene present in the genotype
Describe codominance
as a situation in which both alleles in heterozygous organisms contribute to the phenotype
Explain the inheritance of ABO blood groups:
phenotypes are A, B, AB and O blood groups and alleles are IA, IB and Io
Describe a sex-linked characteristic as
a feature in which the gene responsible is located on a sex chromosome and that this makes the characteristic more common in one sex than in the other
Example of sex- linkage
red-green colour blindness and hemophilia (male) as the have only one X chromosome
