Inheritance Flashcards
What are chromosomes?
- thread-like structure of DNA which carries genetic info of cell
- found in nucleus of animal cells
What is DNA and its structure?
- molecule that contains the genetic instructions for development + function of organism
- double helix structure (sugar phosphate backbone with base pairs AT, GC linked by hydrogen bonds)
What is a gene?
A section of DNA (group of base pairs) that codes for formation of a protein controlling specific characteristic of an organism
What is an allele?
different versions of the same gene
How is sex inherited/determined by genes?
- 1 pair of chromosomes (sex ones) determines sex
- The pair can either be XX for female and XY for male
What is the difference between haploid and diploid?
- haploid cells contain one set of unpaired chromosomes
- diploid cells contain 2 sets of chromosomes with each type having a pair
How many chromosomes do somatic body cells and sex cells have?
- BODY CELLS = 46 chromosomes, 23 pairs
(22 pairs autosomal chromosomes, 1 pair sex chromosome XX, XY) - sex cells = 23 chromosomes
(22 autosomal chromosome, 1 sex chromosome X or Y_
What is mitosis?
cell division that produces 2 genetically identical daughter cells (each 2n)
- used for growth, reproduction of cell
What is meiosis?
cell division producing 4 daughter cells (each n)
- PRODUCES SEX CELLS (gametes)
What are the names of the bases and their pairings?
Adenine - Thymine
Guanine - Cytosine
What are dominant and recessive alleles?
- Dominant gene always shown in phenotype
- recessive is still existent but masked by dominant
(only shown in recessive homozyg. tt)
what is the genotype and phenotype?
Genotype = genetic makeup of organism (ie. TT, Tt, tt)
Phenotype = visible characteristics of organism
What do family pedigrees show?
the inheritance of an allele over generations
What is co-dominance?
- when 2 heterozygous alleles are expressed (ie. blood type A + blood type B = blood type AB)
What is incomplete dominance?
- blending of parent alleles that results in a third phenotype that doesn’t look like either of parents
What is a sex-linked characteristic?
- A characteristic where the gene responsible is located on a sex chromosome
- THEREFORE it is more common in one sex than another (ie. female carriers of colour blindness)
What is a mutation?
- changes to the DNA sequence or chromosome number
- new phenotypes can ONLY appear in a population after a mutation event
What is a mutation?
HOW DOES IT OCCUR AND WORK?!
- changes to the DNA sequence or chromosome number
- new phenotypes can ONLY appear in a population after a mutation event
What are the types of mutation?
- point mutation
- frame shift
- parts or whole chromosome involved
What can cause mutation in genes and chromosomes?
- errors in DNA replication
- errors in cell division
- damage by physical or chemical factors
What are the 3 modes of inheritance?
- Autosomal dominant/recessive
- Sex linked (X linked) dominant recessive
- Incomplete dominane
Why does sex linked inheritance occur?
traits are more common to one gender as the missing arm on Y chromosome means for some trait, only one allele (X) is present and can contribute to phenotype
why can only females be carriers and only men be affected & possess the trait?
- men do not have another allele to dominate over defective allele
- female has another allele inherited from other parent (normal + dom.) but can carry the trait as it is recessive and still existent but masked
what is fertilisation?
union of female and male gametes (sperm + egg) to produce a zygote
What are the processes involved in the formation of a new individual?
- Meiosis
- fertilisation
- mitosis
why do sex cells have half the no. of chromosomes of (somatic) body cells
to maintain the fixed no. of chromosomes in a species, gametes need to have half the no. of chromosomes of a somatic cell
(restored in fertilisation when the gametes fuse to produce zygote)
factors that increase rate of mutations?
- high energy radiation (UV, x-rays, gamma rays)
- carcinogenic chemicals
- extreme heat
causes of mutation
- errors in DNA replication
- errors in cell division
- damage by physical/chemical factors
how mutation can occur
- point mutation
- frame shift
- parts or whole chromosome involved
What is mutation
changes to the DNA sequence or chromosome no.
- new phenotypes can only appear in population after mutation event
what are the 2 types of mutation
- gene mutation: change in the DNA sequence of gene (eg. sickle cell anaemia)
- chromosomal mutation: change in the no. of chromosomes (eg. Down’s syndrome)
what are the genotypes of symbols X^H, X^h, Y
X^HY, X^hY, X^HX^H, X^HX^h, X^hX^h
