Genetics Flashcards
Definition of genome
All the genetic information that A cell must have to function and reproduce as a cell of a particular species
How many chromosomes do we have
I genome consists of 23 pairs of chromosomes that we received from our parents.
One of each chromosome type from each parent.
In general, every cell of my body has a complete set of our individual genome
Homologous
The two members of a pair of chromosomes are called homologues.
Haploid number
Every species has a characteristic number of chromosomes; called its haploid number=n. Humans have n=23 that is we have 23 chromosomes.
We are diploid so we have two pairs (2n) equals 46 total chromosomes or 23 pairs of chromosomes.
The human genome consists of 22 different autosomal chromosomes and two different sex chromosomes X and Y.
Each somatic cell has a diploid complement of chromosomes, gametes (egg and sperm) have a haploid number of chromosomes
Our chromosomes are made up of DNA which is made up of four different nucleotides chemical bases G, A, T and C.
The chromosomes are in the nucleus of all our cells we have 2 copies of each. One copy of each one from mom and copy of each from dad.
If we are male- we have one x (from mom) and one y ( from dad)
If we are female -we have one x (from mom) and one x ( from Dad)
We also have some genes from their mom and dad and our great grandparents and our great great grandparents…how is this info. Passed on?
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What information is stored in our chromosomes
For nucleotidase is G, A, T and C that make a our DNA are arranged in specific patterns throughout our chromosomes. The pattern of the nucleotide will signify a specific set of amino acids which will determine a specific protein product. we call this pattern of nucleotides that code for a specific protein- a GENE.
“Alleles”
The eye color gene have many variations called alleles but the location of the gene and the basic function of the protein it codes for stays the same to give eye color. This is true for all genes.
Variations of a Gene
Homozygous
BB or bb this is called homozygous for this gene
Heterozygous
2 different alleles like Bb ( this is called heterozygous)
The allele pair you have for any gene is called the genotype: BB, Bb, or bb.
The alleles that are expressed depends in part on their dominant or recessive nature. Not all alleles follow this rule but many do. The expression of a genotype is the phenotype- this is what is observed.
If the allele is dominant it will be expressed no matter what the second allele is BB, or Bb.
If the allele is recessive it is only expressed when there re two copies of that allele: bb
Dominant alleles are signified by capital letters and recessive alleles are signified by small letters.
Mitosis
The goal of this process is to produce a copy of genetically identical cells. Cells divide to replace injured or old cells for growth of a multi-cellular organism.
Meiosis
When gametes are formed ( egg and sperm), DNA must be replicated and cell division must occur. This process is called meiosis ( making little “me,s”) and results in cells that are not genetically identical to the parent cell.
Results of meiosis
Gametes Four haploid cells One copy of each chromosome One allele of each gene. Different combinations of alleles for different genes along the chromosomes is possible.
From meiosis we get genetic variability in 2 ways
From meiosis we get genetic variability in / ways:
1) independent assortment of homologous chromosomes.
2) recombination of crossing over of homologous chromosomes during Meiosis I
Recombination/crossing over
Occurs in prophase of meiosis I
Generates diversity
Creates chromosomes with new combinations of alleles for genes a-f
Phenotypes
Which alleles you express will be based on the dominant or recessive nature of each of the alleles present.
Why do cells go through DNA replication
Reproduction, growth/replacement
How can we use segregation patterns in pedigrees to predict the nature of a mutation or a gene?
4 types of inheritance that we will talk about that can be predicted from a pedigree.
Autosomal dominant
Autosomal recessive
Sex- linked
Mitochondrial
Autosomal dominant pedigrees characteristics
- huntingtons disease
- some types of glaucoma
1) affected offspring all have to have at lest one affected parent.
2) 50% of affected persons children are affected
3) unaffected parents never (almost ) produce affected offspring
4) the number of affected males and females are equal
5) disease is transmitted equally from affected males and females.
Autosomal recessive pedigree characteristics
- cystic fibrosis
- Tay-Sachs
- sickle cell
1) affected individuals are usually children of unaffected ( carrier) parents.
2) 25% of the children born of carrier ( heterozygous) parents will be affected.
3) approximately an equal number of males and females affected.
X-linked dominant diseases
-Rett syndrome ( Nero-developmental disorder)
Very few X-linked dominant diseases have been identified.
- Affected males produce only affected females.
- Effective females produce 50% normal and 50% effective offspring.
- Males are usually more severely affected than females.
- Females are more likely to be affected because they have two x’s
- Never passed from father to son
X-linked recessive
- color blindness
- muscular dystrophy
- hemophilia
- Male pattern baldness
1) more males than females show phenotype.
2) affected female will have to receive recessive allele from both mother and father.
3) affected male will only receive allele from mother.
