Inheritance Fe Flashcards
Whats DNA
Building block of genetic material
What is a gene
A segment of DNA that contains Info for the synthesis of a polypeptide that determine a particular characteristic of an organism
What is a chromosome
Compacted form of DNA with proteins containing alleles
When do the traits of dominant allele and recessive allele show
Trait of a dom allele will be expressed as long as one allele is present
Trait of a recessive allele will be expressed when 2 allele is present
Traits of homo chromosomes (4)
Same length
Samer gene loci
Same centromere position
Same genes (can be diff alleles)
What is genotype and phenotype
Genotype is genetic makeup of an organism
Pheno is the observable traits of an organism
Describe Mendel’s 1st law of segregation
• The alleles of a gene exist in pairs, each on separate members of a homologous pair of chromosomes • The homologous chromosomes separate during meiosis resulting in the alleles separating into different gametes • Thus, each gamete contains only one allele of each gene# # Allele pair (diploid condition) is restored when ovum and sperm fuse during fertilisation
What is the test cross for
• A test cross is used to determine the genotype of an organism with dominant trait by crossing the organism with a homozygous recessive organism • If the organism is homozygous dominant, all the offspring should show the dominant trait • If the organism is heterozygous, half the number of offspring should show the dominant trait; The remaining half should show the recessive trait
What happen in complete dominance
• In complete dominance inheritance, the effect of the dominant allele, in a heterozygous genotype completely masks the effect of the other recessive allele
Why would observed ratio differ slightly from expected ratio (2)
– The chance of each offspring receiving a certain allele from their parents is independent of other offspring (random fertilisation)
– The offspring have equal chances of survival
How to make observed ratio nearer to expected ratio
increase no of offsprings
Explain Mendel’s 2nd Law of Independent Assortment (give example)
Each pair of alleles segregate independently of other pairs of alleles
during gamete formation
Eg: the alleles for seed
colour and seed shape sort
into gametes independently
of each other
Codominance
• Occurs when both alleles are equally expressed in the
heterozygous condition
3 characteristics of continuous variation
Traits are brought about by
the combined effects of many genes
No distinct categories,
wide range of intermediates; Traits vary
gradually from one extreme to another
Greatly influenced by the environment
3 char of discontinuous variation
Controlled by a single gene or a few genes
Distinct phenotypes,
no intermediate forms
Rarely/not influenced by the
environment
3 sources of variation
Environment
Meiosis
Mutation
What is Mutation
Refers to either a permanent change in nucleotide sequence of
DNA in the cell of an organism OR a change in the number/
structure of chromosomes
Cause of mutation
result of error during the replication of the gene or
chromosome
Chromosome mutation
Change in the structure or number of chromosomes
Gene mutation and what it produces
Permanent change in the sequence of nucleotides in the DNA
Produces variation between individuals as it results in new alleles of genes
Mutations can be greatly increased by _______ such as: (3)
mutagens
radiations
chemicals
infections agents such as viruses
Effect of gene mutation
The sequence of nucleotides determines the sequence of amino
acids in a polypeptide chain
• Change in nucleotide sequence –>
Change in amino acid sequence -> Change in protein structure –> Non-functional protein
Sickle cell anemia caused by ______
mutation in the gene controlling haemoglobin production
Nondisjunction
• Occurs when homologous chromosomes (during meiosis I) or
sister chromatids (during meiosis II) fail to separate
• This results in some gametes having an extra chromosome
• This abnormal gamete fuses with a normal gamete,
resulting zygote will have an extra chromosome
