Genetics

Question 0

Definition of genome

Answer 0

All the genetic information that A cell must have to function and reproduce as a cell of a particular species

Question 1

How many chromosomes do we have

Answer 1

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

Question 2

Homologous

Answer 2

The two members of a pair of chromosomes are called homologues.

Question 3

Haploid number

Answer 3

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.

Question 4

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

Answer 4

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.

Question 5

If we are male- we have one x (from mom) and one y ( from dad)

Answer 5

If we are female -we have one x (from mom) and one x ( from Dad)

Question 6

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?

Answer 6

??

Question 7

What information is stored in our chromosomes

Answer 7

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.

Question 8

“Alleles”

Answer 8

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

Question 9

Homozygous

Answer 9

BB or bb this is called homozygous for this gene

Question 10

Heterozygous

Answer 10

2 different alleles like Bb ( this is called heterozygous)

Question 11

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.

Answer 11

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.

Question 12

Mitosis

Answer 12

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.

Question 13

Meiosis

Answer 13

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.

Question 14

Results of meiosis

Answer 14

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.

Question 15

From meiosis we get genetic variability in 2 ways

Answer 15

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

Question 16

Recombination/crossing over

Answer 16

Occurs in prophase of meiosis I

Generates diversity

Creates chromosomes with new combinations of alleles for genes a-f

Question 17

Phenotypes

Answer 17

Which alleles you express will be based on the dominant or recessive nature of each of the alleles present.

Question 18

Why do cells go through DNA replication

Answer 18

Reproduction, growth/replacement

Question 19

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.

Answer 19

Autosomal dominant
Autosomal recessive
Sex- linked
Mitochondrial

Question 20

Autosomal dominant pedigrees characteristics

• huntingtons disease
• some types of glaucoma

Answer 20

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.

Question 21

Autosomal recessive pedigree characteristics

• cystic fibrosis
• Tay-Sachs
• sickle cell

Answer 21

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.

Question 22

X-linked dominant diseases

-Rett syndrome ( Nero-developmental disorder)

Answer 22

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

Question 23

X-linked recessive

• color blindness
• muscular dystrophy
• hemophilia
• Male pattern baldness

Answer 23

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.

Question 24

Continuous variation

Answer 24

Traits controlled by two or more genes that are additive and can be quantified. Ex, size, weight, height, and color.

What traits would you suspect are controlled by more than one gene??
How will the environment affect these traits ??

Question 25

Genetic disorders: familial or somatic?

Answer 25

Mutations leading to disease can be caused by somatic mutations ( mitosis) or germ line mutations ( meiosis)
The ability to identify which type of mutation has occurred is vital in predicting whether or not the trait will be passed on.

Question 26

DNA EXPRESSION:when a gene is activated-mRNAis synthesized. this process is called transcription

Answer 26

Many things need to happen in order to have expression

Question 27

Translation:

Answer 27

Process in which the DNA code transcribed into mRNA is read in 3letter words called codons.

Each of the 64 codons represents one of 20 possible amino acids or one of 3 stop,codons.

Question 28

What happens when cell division, DNA replication, transcription or translation goes wrong?

Answer 28

Mutations occur as a gain or loss of whole chromosomes.
Anueploidy ( Down syndrome 47-xy ( trisomy 2n + 1 chromosome), turners syndrome XO, klinefelters xxy)
This occurs through nondisjunction in meiosis and mitosis

Question 29

Trisomy

Answer 29

Down syndrome ( 47, +21)
-characteristic facial patterning, mental retardation
1/800 live births
95% of these trisomes have defective egg as source.
-prone to respiratory disease, etc.
Detectable by amincentesis or chronic villus sampling (cvs) or chemical tests.

Question 30

Mutations at the nucleotide level

Answer 30

-base substitution/ point mutation/SNP
(Sickle cell anemia, Tay Sachs, cystic fibrosis)
Point mutation in the beta chain of hemoglobin
The HBB gene produces one of the subunits of hemoglobin, the protein that enables red blood cells to carry oxygen to all,parts of the body. The mutated HBB gene produces defective hemoglobin, which distorts red blood cells into a sickle crescent shape.

Question 31

Deletions and insertion mutations

Answer 31

Deletions and insertions are emerging as a major cause of genetic disorders.
5-10 % of all know mutations are addition or loss of nucleotides.
Ex- huntingtons, fragile x myotonic dystrophy (triplet repeat syndromes)

Primary consequence is a shift in the reading frames of DNA sequence aka frame-shift mutations

Question 32

Medical applications

Answer 32

Change in gene expression associated with a specific disease
Mutation detection ( single base, such as one type of diabetes)
Polymorphism analysis ( multi factorial diseases, such as breast cancer- correlations sought between diseases and SNPs:
Pharmacogenomics ( the search for therapeutic responses to drugs given the genetic profiles of patients)