Ch 17 - (Inheritance) Flashcards
What is inheritance?
Transmission of genetic information from generation to generation.
Where are chromosomes located?
Nucleus of the cell
What is a gene?
A short length of DNA found on a chromosome that codes for a specific protein
What do genes do?
- Control our characteristics
- code for proteins
what are alleles?
Different versions of a particular gene
- gives characteristics
what is sex determined by?
Entire chromosome pair
What is the female sex chromosome?
XX
What is the male sex chromosome?
XY
who is responsible for gender of child?
- only father passes Y chromosome
Why is father responsible for determining the gender?
- he ejaculates 250 million sperms during sexual intercourse
- only 125 million sperms carry X chromosome
- if one of these sperms fertilize egg, fetus will be female
- 125 million sperms carry Y chromosome which will result in a boy
How can the inheritance of gender be shown?
- Genetic diagram
- Punnett Square
what does the DNA base sequence determine?
- Amino acid sequence in protein
- DNA (a series of bases) is converted into proteins (amino acids )
What are the 2 stages of protein synthesis?
- Transcription: Rewriting the base code of DNA into bases of RNA
- Translation: Using RNA base sequence to build amino acids into sequence in a protein
What are proteins made by?
- Ribosomes with the sequence of amino acids controlled by the sequence of bases contained within DNA
Explain the process of protein synthesis.
- DNA cannot travel out of the nucleus to the ribosomes (too big to pass through a nuclear pore) so base code of each gene is transcribed into RNA molecule called messenger RNA (mRNA)
- mRNA mass then moves out of the nucleus and attaches to ribosome
- ribosome ‘reads’ the code on the mRNA groups of three
- each triplet of bases codes for a specific amino acid
- ribosomes translate the sequence of bases into sequence of amino acids that make up a protein
- Once ands, it releases from ribosome so it can fold and form the final structure
What does expression of a gene mean?
Whether that gene is transcribed and translated in a particular cell or not
How and why are most genes not expressed in a particular cell?
- they are switched off
- cuz it’s waste of energy and other resources in the cell
Which proteins are used for protein synthesis?
- only gene whose protein are vital to the cell’s functions are expressed (switched on)
What does DNA do in protein synthesis?
- controls cell function
- controlling production of proteins
What’s re the diff types of proteins that can be synthesized?
Enzymes, antibodies, receptors, neurotransmitter
Why are many genes in a particular cell not expressed?
The cell only make specific proteins it needs
How many chromosomes are there in each cell
23 diff chromosomes pair
46 in total chromosomes
What is a diploid and haploid cell?
Diploid nuclei: Nuclei with 2 sets of chromosomes
Haploid nuclei: One set of unpaired chromosomes
How many chromosomes does each chromosome consist of?
23 chromosomes
What is mitosis?
The type of cell division is used for growth, repair of damaged tissues, replacement of cells and asexual reproduction.
Define mitosis.
Nuclear division giving rise to genetically identical cells
What is the process before mitosis happens?
- each chromosome in the nucleus copies itself (forms X shaped chromosome)
- chromosomes line up along the center of the cell where cell fibers pull them apart.
- cell divides into 2, each new cell has a copy of each chromosome
What is the importance of mitosis?
- all cells in the body (excluding gametes) are produced by mitosis of the zygote
- important for replacing cells and for growth
What does mitosis occur in?
- Growth: Mitosis produce new cells
- Repair: To replace damaged or dead cells
- Asexual reproduction: Mitosis produces offspring that’s re genetically identical to parent
What do many tissues in the body contain?
Unspecialized cells (stem cells)
What is the function of stem cells?
Produce new daughter cells that can become specialized within tissue
What is the ultimate stem cell?
Zygote (Embryonic stem cells) - becomes a ball of unsoecialised cells
Define meiosis
Nuclear division that gives rise to cells that are genetically different
What is meiosis used for?
To produce gametes (sex cells)
What needs to happen when gametes (sex cells) are formed?
Chromosome must be halved
When does halving of chromosomes happen?
- Meiosis
- reduction division
- chromosome number is halved from diploid to haploid
- results in genetically different cells
What happens in meiosis?
- chromosomes double in mitosis and line up in center of cell
- cells divide twice so that only one copy of chromosomes is passed onto each gamete
What happens in double division?
- Gametes are haploid
- thsi double division, meiosis produces 4 haploid cells
Explain the proper process of meiosis.
- each chromosome makes a copy of itself (X - chromosome)
- First division: Chromosome pair up along the cell, recombination occurs, cell fibers pull each pair apart, each new cell has one recombinant chromosome pair
- Second division: Chromosome will line up along the centre of the cell, cell fibres will pull them apart (mitosis)
- 4 haploid daughter cells
What is the importance of meiosis?
- Production of gametes
- increases genetic variation
- has variation and has new combinations of maternal and paternal chromosomes
What is the difference in the cells produced in mitosis and meiosis?
Mitosis: 2 cells produced (daughter cells)
Meiosis: 4 cells produced (daughter cells)
What is the difference in the daughter cells produced in mitosis and meiosis?
Mitosis: Diploid
Meiosis: Haploid
What is the difference in the daughter cells characteristics produced in mitosis and meiosis?
Mitosis: Genetically identical to each other n parent cell
Meiosis: Genetically different from each other n parent cell
What is the difference in the cell division in mitosis and meiosis?
Mitosis: 1 cell division
Meiosis: 2 cell division
What is a phenotype?
Observable characteristics of an organism (like eye color or blood type)
What is a genotype?
combination of alleles that control each characteristic
What’s re the 2 types of alleles?
- Dominant
- Recessive
What does a dominant allele do?
Only needs to be inherited from one parent
What does a recessive allele do?
needs to be inherited from both parents
what is the term used to talk about if two people have 2 alleles of a gene that’s re the same?
Homozygous
What are the 2 types of homozygous?
- Homozygous dominant (having 2 copies of dominant allele)
- Homozygous recessive (Having 2 copies of recessive allele)
what is the term used to talk about if two alleles of a gene are different?
Heterozygous
How is a dominant allele and recessive allele written?
Dominant: Capital letters
Recessive: Lower case
What happens when 2 identical homozygous reproduce together?
- Produce offspring with exactly the same genotype & phenotype as parents
- pure breeding
What happens when a heterozygous person reproduces?
Produce offspring with different alleles, genotypes, and phenotype than parents
Not pure breeding
What is monohybrid inheritance?
Inheritance of characteristics controlled by a single gene (Mono = 1)
How can monohybrid inheritance be determined?
- Punnett Square
- possible combination of alleles
- ratio to be worked out
How do u construct Punnett square?
- Determine parental genotype
- Select a letter (diff lower case)
- Split allele for each parent, add to punett Square around the outside.
- Fill in middle 4 squares
What should you do when u are asked to comment on the ratio of different allele combinations?
Calculate a percentage chance of offspring showing specific characteristics
What are family pedigree charts used for?
trace pattern of inheritance of a specific characteristic through generations of a family
What are the following shales representative of in a pedigree chart:
- Square
- Circle
- Red
- Blue
- Square - male
- Circle - female
- Red - affected
- Blue - unaffected
How do u identify an unknown genotype?
- test cross
- cross an unknown individual with recessive phenotype (genotype is homozygous recessive)
- ratio of phenotypes in the offspring
What is codominance?
Both alleles in heterozygous organisms contribute to phenotype
What is an example of codominance?
inheritance
What does I, A, B, and O represent?
I = gene
A, B, O = alleles
What alleles codependent?
I^A and I^B are codominant but I^O is dependent
What does I^A result in?
antigen A in blood
What does I^B result in?
antigen B in blood
What does I^O result in?
no antigens in the blood
What are alleles on the same chromosome said to be?
Linked
What do alleles control?
- Particular characteristics that are found on sex chromosomes
- sex linked
Why are males more likely to show sex linked recessive cells?
- Only have one X chromosomes
- more likely to show sex linked recessive conditions
Why are X alleles more prone to sex- linked recessive conditions?
Only alleles on the X chromosome because Y chromosome is much smaller
What about females’ recessive sex- linked conditions?
- carrier
-have 2 copies of X chromosome and are likely to inherit one dominant allele that masks effect on recessive cell
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