Unit 17 - Inheritance Flashcards
location of genetic information in DNA
Genes
Gene
Length of DNA that codes for a particular protein
Alleles
Alternative versions of each gene
Two types of sex chromosomes
X & Y
Haploid nucleus
- Nucleus of a gamete
- Has 23 chromosomes
Diploid nucleus
- Nucleus of a body cell
- Has 46 chromosomes (23 pairs)
Location of chromosomes
Nucleus of a cell
Male sex chromosomes
XY
Female sex chromosomes
XX
Sex chromosome of a sperm cell
X or Y
Sex chromosome of an egg cell
X
Four bases in DNA
- A
- T
- C
- G
Shape of DNA
Double helix
Complementary base pairs
- A & T
- C & G
Genetic code
- Sequences of bases in a gene
- Determines the order that amino acids are joined to make a specific protein
Proteins that can be made from gene expression
- Enzymes
- Antibodies
- Receptors for neurotransmitters
Location of protein synthesis
Ribosomes in the cytoplasm
mRNA
- Messenger RNA
- Transports information of DNA because DNA is too large to move out the nucleus
- Similar but base T is replaced with U
Stages of protein synthesis
- DNA molecule in the nucleus unzips, exposing the bases in a gene
- mRNA molecule is formed by the exposed bases as a template and the bases in the mRNA pair with the complementary bases in DNA to carry a copy of the gene
- mRNA molecule moves out the nucleus into the cytoplasm
- Ribosome reads mRNA code and joins amino acids to form a protein following the sequence of bases
Mitosis
A type of nuclear division that gives rise to genetically identical cells
Cells produced by nuclear division
Daughter cells
Occurrences in mitosis
- Chromosomes are replicated exactly so there are two copies
- Nucleus of the cell divides into two with one copy of each chromosome in each new cell
Stem cells
- Unspecialized cells that divide by mitosis
- Cells can differentiate to become specialized for a particular function
Location of stem cells
Embryos, umbilical cords, adult bone marrow
Examples of mitosis
- Growth
- Preparing damaged tissue after injury
- Asexual reproduction
Meiosis
A type of nuclear division that gives rise to cells that are genetically different
Use of meiosis
- Production of gametes (testicles, ovaries, anthers)
Occurrences in meiosis
- Each chromosome is exactly duplicated
- Number of chromosome is halved- reduction division
- Diploid cell becomes four haploid cells
- Cross over forms variation where the chromosomes in a pair swap parts with each other making two new chromosomes
Inheritance
The transmission of genetic information from generation to generation
Homozygous
If there are two identical alleles in a gene
Heterozygous
If there are two different alleles in a gene
Phenotype
The observable features of an organism
Genotype
The genetic make-up of an organism in terms of its alleles
Pure-breeding
When two identical homozygous individuals breed together and the offspring inherits the same alleles
Monohybrid cross
Breeding of two individuals that differ in their alleles for a particular gene
Dominant allele
Always expressed if present
Recessive allele
Only expressed if the dominant allele is not present
Notation for dominant and recessive alleles
- Dominant uses uppercase
- Recessive uses lowercase
Carriers
Individual who carries one copy of a recessive allele for a genetic characteristic
Genotype used in a test cross
Homozygous recessive
Codominance
Where two different alleles for a characteristic influence the phenotype to the same extent
Genotypes of blood
- A
- B
- AB
- O
- Shows A & B are codominant and A & B are dominant to O
Inherited characteristics from sex chromosomes
Sex-linked characteristics
Examples of sex-linked characteristics
- Hemophilia
- Red-green color blindness
- Alleles are carried in X chromosome
Reason for sex-linked characteristics
- The Y chromosome is shorter are carrier genes that aren’t in X
- Or X is longer and carrier many more genes that are not found in Y
Alleles for colorblindness
- R is dominant normal vision
- r is recessive colorblindness
