17. Inheritance Flashcards
What are chromosomes made of?
DNA
What does DNA contain?
genetic information in the form of genes
What is a gene?
a length of DNA that codes for a protein
Where is genetic information in the form of genes contained?
DNA
A length of DNA that codes for a protein is…
a gene
What is an allele?
an alternative form of a gene
A girl would have ____ chromosomes.
XX
An alternative form of a gene is…
an allele
A boy would have _____ chromosomes.
XY
What is a chromosome?
thread-like structure of coiled DNA
What is DNA? What does it do?
- a large molecule made from bases
- carries genetic information in the form of genes
Which gametes are contained in sperm cells?
X or Y
Which gametes are contained in egg cells?
X
What is the structure of DNA?
- two strands coil together to form double helix
- each strand contains bases (chemicals)
What is a genetic code?
the sequence of bases in a gene
What does the genetic code determine?
the sequence of amino acids used to make a specific protein
What determines the sequence of amino acids used to make a specific protein?
the sequence of bases in a gene
What does the sequence of bases in a gene determine?
the sequence of amino acids used to make a specific protein
What gives different shapes to protein molecules?
different sequences of amino acids
Different sequences of amino acids give…
different shapes to protein molecules
What is the role of DNA?
controlling cell function by controlling the production of proteins
What are some types of protein?
- enzymes
- membrane carriers
- antibodies
- receptors for neurotransmitters
Explain how a protein is made.
- a DNA molecule in the nucleus unzips, exposing the bases in a gene
- mRNA molecule formed using the exposed bases of the DNA strand as a template
- bases in mRNA molecule pair with complementary bases in the DNA, so the mRNA molecule now carries a copy of the gene
- mRNA molecule moves out of the nucleus into the cytoplasm
- ribosome reads the mRNA code
- ribosome joins amino acids together to form a protein, following the specific sequence of bases in the mRNA
Why are many genes in a particular cell not expressed?
because the cell only makes the specific proteins it needs
What do most body cells in an organism contain?
the same genes
The same genes are contained in…
most body cells
A cell only makes the specific proteins it needs. Therefore…
many genes in a particular cell are not expressed
What is a haploid nucleus?
a nucleus containing a single set of chromosomes
What is a diploid nucleus?
a nucleus containing two sets of chromosomes
In a diploid cell, there is a pair of each type of ______.
chromosome
How many chromosomes are in a human diploid cell?
23 pairs, 46 chromosomes:
a pair of each type of chromosome
Define mitosis.
nuclear division giving rise to genetically identical cells
What are some roles of mitosis?
- growth
- repair of damaged tissues
- replacement of cells
- asexual reproduction
What determines the sequence of amino acids in a protein?
the sequence of bases on an mRNA molecule
What molecule carries genetic information from the nucleus to the cytoplasm?
mRNA
What must happen before mitosis takes place?
the exact replication of chromosomes
(so that there are two copies of each chromosome when the cell is about to divide)
Outline the process of mitosis.
- two copies of each chromosome are joined together near the middle
- nucleus divides into two
- one copy of each chromosome goes into each new cell
- this keeps the number of chromosomes in the two daughter cells the same as in the original cell
What happens during mitosis?
the copies of chromosomes separate, maintaining the chromosome number in each daughter cell
Define stem cells.
unspecialised cells, divide by mitosis to produce daughter cells. these daughter cells can become specialised for specific functions
What is the role of meiosis?
production of gametes
Describe meiosis.
reduction division: the chromosome number is halved, resulting in genetically different cells
Define inheritance.
the transmission of genetic information from generation to generation
Define genotype.
the genetic make-up of an organism and in terms of the alleles present
The genetic make-up of an organism and in terms of the alleles present is…
the genotype
The transmission of genetic information from generation to generation is…
inheritance
Define phenotype.
the observable features of an organism
The observable features of an organism is…
phenotype
What does the term homozygous mean?
having two identical alleles of a particular gene
What causes pure breeding?
two identical homozygous individuals that breed together
What does the term heterozygous mean?
having two different alleles of a particular gene
Which type of individual will not be pure-breeding?
heterozygous
Heterozygous individuals will NOT be…
pure-breeding
What is a dominant allele?
an allele that is always expressed if it is present in the genotype
What is a recessive allele?
an allele that is only expressed when there is no dominant allele present in the genotype
What is a test cross?
a cross with a homozygous recessive individual
What is a test cross used for?
to determine the genotype of an individual showing the dominant trait, to find out whether it has DD or Dd
What is codominance?
a situation in which both alleles in heterozygous organisms contribute to the phenotype
What is a sex-linked characteristic?
- feature in which the gene responsible is located on
a sex chromosome - makes the characteristic more common in one sex than in the other
What is a an example of sex linkage?
red-green colour blindness
