inheritance (topic 17) Flashcards
chromosome
DNA in the nucleus of a cell is coiled and packed to form a thread-like structure,
chromosomes are made of DNA,
which contains genetic information in the form
of genes
gene
a length of DNA that codes for a
protein
dna
A large molecule made from bases, and which carries genetic information in the form of genes.
allele
An alternative version of a gene. A section of DNA that codes for a particular protein
what is the chromosome responsible for sex
XY chromsomes
xx= female
xy= male
haploid nucleus
a nucleus containing a single set of unpaired chromosomes. eg. gamete= 23 chromosomes
diploid nucleus
a nucleus containing two sets of chromosomes, for example in body cells.= 46 chromosomes (23 pairs)
how is sex inherited
each person inherits one sex chromsome from father and one from mother
sperm cell is either x or y
egg is always x
describe dna
two strands that coil together to form a double helix each strands contain complementary chemical substances called bases
T-A
C-G
genetic code
The sequence (order) of bases differs from gene to gene. The sequence of bases in a gene is its genetic code: it determines the order in which amino acids are joined together to make a specific protein
what does the sequence of bases in a gene determine
the sequence of amino acids used to
make a specific protein and different sequences of amino acids result in different shaped 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
describe process of making proteins (protein synthesis)
-protein syntehsis occurs in ribosomes found in the cytoplasm
1. dna moelcule in nucleus unzips, exposing bases in gene
2. Mrna molecule formed using exposed bases in unzipped dna strand as template, bases in mrna bind with complementary bases in dna, mrna molecule carries a copy of the gene
3. mrna molecule moves out of the nucleus into the cytoplasm
4.ribosome reads mrna codes and joins amino acids to form protein follwoing specific base sequence in the mrna
true or false most body 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
true
mitosis
nuclear division giving rise to
genetically identical cells, cells produced are called daughter cells
fucntions of mitosis
cell repair/ replacement, assexual reproduction, tissue repair,
describe path leading to mitosis
- each chromosome is replicated exactly so that there are two copies of each chromosome
- chromosome join together into middle of cell
- when nucleus divides into two, a copy of each chromosome goes into each new cell
stem cells
unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions
meiosis
reduction division in which the chromosome number is halved from diploid involved in production of gametes
where are male gametes and female gametes produced
feamle- ovaries
male- testes
inheritance
the transmission of genetic information from generation to generation
phenotype
observable feature of an orgnaism
genotype
genetic make-up of an organism in terms of its alleles
homozygous
two identical alleles
heterozygous
two different alleles
pure breeding
two identical homozygous individuals
that breed together will be pure-breeding all their offspring will inherit the same alleles, and show the same phenotype as their parents
monohybrid cross
Breeding two individuals that differ in their alleles for a particular gene.
dominant allele
always expressed if it is present (uppercase letter symbol)
recessive allele
only expressed if the dominant allele is not present. (lower case letter symbol)
pedigree diagram
A type of family tree that shows the inheritance of a feature.
squares= males
circles= females
what is meant by a carrier
An individual who has a single copy of a recessive allele that is responsible for a genetic disorder or disease.
test cross
A cross with a homozygous recessive individual, used to determine the genotype of an individual showing the dominant trait.
codominance
A situation in which two different alleles for a gene influence the phenotype to the same extent, for example in human ABO blood groups.
what are the alleles for blood
I^a I^b I^o
sex linked characteristic
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 eg. red green color blindness
describe red green colour blindness
sex linked chcaractersitic carried in x chromsome, which is recessive, meaning feamles have a fewer chance of getting the disease, as man only need to inherit one copy of the gene to gain the disease, while feamles must carry both, if only one recessive gene present female is a carrier
